Sorry, I can’t find the key ______ the lock. How can we open the door?[ ]

In class the students put their books _____ their desks. [ ]

Thank you________the great photo_______your family.[ ]

She looks sad. Do you know why?—Her son went to study in Canada. I think she _________ him.

I used to spend all my pocket money on clothes and snacks. But now, I try to ______ some money for charities.