I’d like to send this letter ______ England ______ air. [ ]

I left my knife on the ______ /te??bl/ last night, but I forgot it.

Volunteering is becoming popular in China .— Yeah, people are now aware that helping others is helping themselves.

In our school library, there a number of books on science and the number of the books growing larger and larger.

will the manager come back’?—Maybe in three days.[ ]