________a teacher has given permission is a student allowed to enter the classroom.

We students can _______ food and old clothes to the homeless people, and the teachers can __________ learning skills for the poor children.

This young tree could not have been damaged ______accident; I believe it was done _____ purpose

John did the task____ his sister

David has won the first prize insinging; he is still very excited now and feels________ desire to go to bed.