Dentists always tell people ______ too many sweets.

--- Excuse me sir, where is Room 301?--- Just a minute. I’ll ask Bob ________ you to your room.

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

It took_______an hour_______to the park last Saturday.

In order _______ his English，he joined an English club.