Teenagers should do what they can ________ their achievements.

We must do everything we can          waste water from running into rivers.

—I left my keys in my office. Could you help me ___        them?—OK．I’ll do it at once．

His father told him ________ his best friend to dinner this Sunday.

—Could you tell me how to improve spoken English?—Well, just take every chance to practice ________ and don’t be shy.