If a computer crashes,you will lose the file you _____ on unless you save it regularly.

In my class some students love music, are fond of drawing and enjoy reading.

Mary is very shy. She goes out and she has few friends.

He is a good student. He _____hislessons.

It’s wise _______ you _______your child at home alone while it’s also very important _______ him to learn toprotect himself.