把下列句子改成被动语态
问题描述：
把下列句子改成被动语态
1.Do the workers build many buildings?
2.What does the teacher often tell the boy to do
3.How many desks do the buy every term?
答
1.Are many buildings built by the workers
2.What is the boy often told to do by the teacher
3.How many desks are bought by them every term?