The teacher is busy ____ teaching.

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

We go to school ____ a bike.          

A.in                B.on              C.by             D.ove

To understand the grammar of the sentence，you must break it______ into parts． 

A．down          B．up          C．off           D．out

 2. “_____ when does the pub stay open？”  “About midnight.”

    A. Since. B. Before

    C. Until. D. After

The trouble is ____ we can not find such an expert.

A. why                 B. that                  C. where                  D. /

They were surprised that a child should work out the problem they themselves couldn’t．

A．once B．then C．while D．if

 11. The chemistry teacher required the students _______ more attention _______ the lab clean.

A. to pay, to keep     B. to paying, to keeping  C. to pay, to keeping      D. paying, keeping

We have produced 15% more cotton this year____ we did last year.

A. as                B. than           C. like            D. white

Write clearly ____ your teacher can understand .you correctly.

A. since            B. for           C. because                      D. so that

Some people say that we live _____ the age of computers.

A. in 　　                 B. at 　　                      C. with 　　          D. for