Though they are far away from school, the children who live in mountains ______ go to school on foot.

Hello, Mary! This is John. You must know why I _________ you.－Oh, hello, John! I’ve waited for this call since last month.

The old man could cross the busy street _____ the help of his dog. [ ]

I forgot to bring my pen, would you please lend ________ to me?

Do you find _______ difficult to be independent(独立的)?.