I can't use your pen, ___ there is no ink in it.                   A. for    B. when   C. if    D. whether 

I’ll discuss it with you ____ you like to come. 

A. when                          B. where                          C. whoever                       D. whenever

If you are worried about the problem，you should do something it．

A．a(chǎn)bout B．for C．a(chǎn)gainst D．with

You must work hard,____ you will not learn English well.

A. if                         B. whether              C. otherwise        D. unless

We arrived at the station ____ the train had left.

A. after            B. before          C. since          D. when

Let's walk over ___the shop on the other side of the street.

A. in                         B. to                           C. under                D. by   

Something must be done to prevent our city ____ by thick smoke.

A. to be polluted      B. from polluting     C. from being polluted D. polluting

The teacher is busy ____ correcting papers.

A. for                    B.in                   C.on             D.of

It's very kind____ you to repair the bike ____ me.

A.for.for           B.of,of                           C.of,for                            D.for,of

Letterboxes are much more _______ in the UK than in the US, where most people have a mailbox instead.

  A. common            B. normal           C. ordinary       D. usual