2. Can you imagine the difficulty that he had _____ the problems?

A. to work out　　　　　　　　　 B. work out

C. worked out　　　　　　　　　 D. working out

第一节：单项选择。(每小题1分，共20分)

1. This is a _____ book that you may _____ in daily English study.

　 A .referring; refer to　　　　　　　 B. referring; refer

C. reference; refer to　　　　　　　 D. reference; refer