Choose the correct sentence which is built from the words and phrases given:
My sister/ willing/ help/ our mother/ housework/ when/ holiday.
My sister was willing to help our mother for the housework when she had a holiday.
My sister was willing to help our mother with the housework w hen she had a holiday.
My sister was willing to help our mother at the housework when she had a holiday.
My sister was willing to help our mother on the housework when she had a holiday.
My sister was willing to help our mother on the housework when she had a holiday.