Choose the correct sentence which is built from the words and phrases given:
Developing countries/ need/ do/ research/ find/ solutions/ agriculture/ problems.
Developing countries need doing research to find solutions to agriculture problems.
Developing countries need to do research to find solutions to agriculture problems.
Developing countries need to do researching to find solutions to agriculture problems.
Developing countries need to do research to finding solutions to agriculture problems.
Developing countries need to do research to find solutions to agriculture problems.