Các nguyên tố nhóm halogen có cấu hình electron lớp ngoài cùng là

Read the following pasage and mark the letter A, B, C or D to indicate the correct answer to each of the questions:

 In science, a theory is a reasonable explanation of observed events that are related. A theory often involves an imaginary model that helps scientists picture the way an observed event could be produced. A good example of this is found in the kinetic molecular theory, in which gases are pictured as being made up of many small particles that are in constant motion. 

 A useful theory, in addition to explaining past observation, helps to predict events that have not as yet been observed. After a theory has been publicized, scientists design experiments to test the theory. If observations confirm the scientists' predictions, the theory is supported. If observations do not confirm the predictions, the scientists must search further. There may be a fault in the experiment, or the theory may have to be revised or rejected.

 Science involves imagination and creative thinking as well as collecting information and performing experiments. Facts by themselves are not science. As the mathematician Jules Henri Poincare said: "Science is built with facts just as a house is built with bricks, but a collection of facts cannot be called science any more than a pile of bricks can be called a house." 

 Most scientists start an investigation by finding out what other scientists have learned about a particular problem. After known facts have been gathered, the scientist comes to the part of the investigation that requires considerable imagination. Possible solutions to the problem are formulated. These possible solutions are called hypotheses. In a way, any hypothesis is a leap into the unknown. It extends the scientist's thinking beyond the known facts. The scientist plans experiments, performs calculations, and makes observations to test hypotheses. For without hypotheses, further investigation lacks purpose and direction. When hypotheses are confirmed, they are incorporated into theories. 

Question: “Bricks” are mentioned in paragraph 3 to indicate how _______.         

Số hạng không chứa x trong khai triển là:

Read the following pasage and mark the letter A, B, C or D to indicate the correct answer to each of the questions:

 In science, a theory is a reasonable explanation of observed events that are related. A theory often involves an imaginary model that helps scientists picture the way an observed event could be produced. A good example of this is found in the kinetic molecular theory, in which gases are pictured as being made up of many small particles that are in constant motion. 

 A useful theory, in addition to explaining past observation, helps to predict events that have not as yet been observed. After a theory has been publicized, scientists design experiments to test the theory. If observations confirm the scientists' predictions, the theory is supported. If observations do not confirm the predictions, the scientists must search further. There may be a fault in the experiment, or the theory may have to be revised or rejected.

 Science involves imagination and creative thinking as well as collecting information and performing experiments. Facts by themselves are not science. As the mathematician Jules Henri Poincare said: "Science is built with facts just as a house is built with bricks, but a collection of facts cannot be called science any more than a pile of bricks can be called a house." 

 Most scientists start an investigation by finding out what other scientists have learned about a particular problem. After known facts have been gathered, the scientist comes to the part of the investigation that requires considerable imagination. Possible solutions to the problem are formulated. These possible solutions are called hypotheses. In a way, any hypothesis is a leap into the unknown. It extends the scientist's thinking beyond the known facts. The scientist plans experiments, performs calculations, and makes observations to test hypotheses. For without hypotheses, further investigation lacks purpose and direction. When hypotheses are confirmed, they are incorporated into theories. 

Question: In the fourth paragraph, the author implies that imagination is most important to scientists when they _______.         

Lớp có học sinh giỏi trong đó có nam và  nữ. Lớp có học sinh giỏi trong đó có nam và nữ. Cần chọn mỗi lớp học sinh giỏi đi dự Đại hội Thi đua. Hỏi có bao nhiêu cách chọn sao cho trong học sinh được chọn có nam và nữ ?

Cho tập có phần tử. Hỏi tập có bao nhiêu tập hợp con khác rỗng mà có số phần tử chẵn.           

Read the following pasage and mark the letter A, B, C or D to indicate the correct answer to each of the questions:

 In science, a theory is a reasonable explanation of observed events that are related. A theory often involves an imaginary model that helps scientists picture the way an observed event could be produced. A good example of this is found in the kinetic molecular theory, in which gases are pictured as being made up of many small particles that are in constant motion. 

 A useful theory, in addition to explaining past observation, helps to predict events that have not as yet been observed. After a theory has been publicized, scientists design experiments to test the theory. If observations confirm the scientists' predictions, the theory is supported. If observations do not confirm the predictions, the scientists must search further. There may be a fault in the experiment, or the theory may have to be revised or rejected.

 Science involves imagination and creative thinking as well as collecting information and performing experiments. Facts by themselves are not science. As the mathematician Jules Henri Poincare said: "Science is built with facts just as a house is built with bricks, but a collection of facts cannot be called science any more than a pile of bricks can be called a house." 

 Most scientists start an investigation by finding out what other scientists have learned about a particular problem. After known facts have been gathered, the scientist comes to the part of the investigation that requires considerable imagination. Possible solutions to the problem are formulated. These possible solutions are called hypotheses. In a way, any hypothesis is a leap into the unknown. It extends the scientist's thinking beyond the known facts. The scientist plans experiments, performs calculations, and makes observations to test hypotheses. For without hypotheses, further investigation lacks purpose and direction. When hypotheses are confirmed, they are incorporated into theories. 

Question: In the last paragraph, what does the author imply is a major function of hypotheses?         

Read the following passage and mark the letters A, B, C or D on your answer sheet to indicate the correct answer to each of the questions: 

This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, new audiences all emerged in the literature of this half century.

As a result, at the onset of World War I, the spirit and substance of American literature had evolved remarkably, just as its center of production had shifted from Boston to New York in the late 1880s and the sources of its energy to Chicago and the Midwest. No longer was it produced, at least in its popular forms, in the main by solemn, typically moralistic men from New England and the Old South; no longer were polite, well-dressed, grammatically correct, middle-class young people the only central characters in its narratives; no longer were these narratives to be set in exotic places and remote times; no longer, indeed, were fiction, poetry, drama, and formal history the chief acceptable forms of literary expression; no longer, finally, was literature read primarily by young, middle class women.

In sum, American literature in these years fulfilled in considerable measure the condition Walt Whitman called for in 1867 in describing Leaves of Grass: it treats, he said of his own major work, each state and region as peers "and expands from them, and includes the world ... connecting an American citizen with the citizens of all nations." At the same time, these years saw the emergence of what has been designated "the literature of argument," powerful works in sociology, philosophy, psychology, many of them impelled by the spirit of exposure and reform. Just as America learned to play a role in this half century as an autonomous international political, economic, and military power, so did its literature establish itself as a producer of major works.

Question: The word “exotic" in paragraph two is closest in meaning to________.    

Có 3 bi xanh, 3 bi đỏ, 3 bi trắng và 3 bi vàng (các viên bi cùng màu giống nhau). Hỏi có bao nhiêu cách xếp 12 viên bị thành một hàng ngang sao cho các bi cùng màu không cạnh nhau?           

Cho  là số tự nhiên thỏa mãn  Khẳng định nào sau đây đúng?

Read the following passage and mark the letters A, B, C or D on your answer sheet to indicate the correct answer to each of the questions: 

This rapid transcontinental settlement and these new urban industrial circumstances of the last half of the 19th century were accompanied by the development of national literature of great abundance and variety. New themes, new forms, new subjects, new regions, new authors, new audiences all emerged in the literature of this half century.

As a result, at the onset of World War I, the spirit and substance of American literature had evolved remarkably, just as its center of production had shifted from Boston to New York in the late 1880s and the sources of its energy to Chicago and the Midwest. No longer was it produced, at least in its popular forms, in the main by solemn, typically moralistic men from New England and the Old South; no longer were polite, well-dressed, grammatically correct, middle-class young people the only central characters in its narratives; no longer were these narratives to be set in exotic places and remote times; no longer, indeed, were fiction, poetry, drama, and formal history the chief acceptable forms of literary expression; no longer, finally, was literature read primarily by young, middle class women.

In sum, American literature in these years fulfilled in considerable measure the condition Walt Whitman called for in 1867 in describing Leaves of Grass: it treats, he said of his own major work, each state and region as peers "and expands from them, and includes the world ... connecting an American citizen with the citizens of all nations". At the same time, these years saw the emergence of what has been designated "the literature of argument," powerful works in sociology, philosophy, psychology, many of them impelled by the spirit of exposure and reform. Just as America learned to play a role in this half century as an autonomous international political, economic, and military power, so did its literature establish itself as a producer of major works.

Question: The word “evolved” in paragraph two is closest in meaning to________.