By the time he was twelve he ______ a chemistry lab of his own.　 A. built 　 B. has built  C. had built 　 D. was building

I like reading poems, because poems can ___certain ____.

   A. convey; emotion                       B. convey; emotions  

   C. express; emotions                     D. explain; emotions

The　medicine　is　on　sale　everywhere．You　can　get　it　at＿＿chemist's．

A)each　          B)some　           C)certain　       D)any

Last term our maths teacher set so difficult an examination problem _____ none of us worked out.

　 A. that 　 B. as   C. so that 　 D. which

　　I’ve worked with children before, so I know what ______ in my new job.

　　A. expected　B. to expect　C. to be expecting　　D. expects