20、______ is known to all is that while driving drivers should keep an eye out for road signs, on which are words or symbols giving directions or other traffic instructions.

A. What      B. As        C. It         D. Which

19、      with a difficult situation，Arnold decided to ask his boss for advice．

A．To face        B．Having faced        C．Faced        D．Facing

18、You’d better take a pen when you go to the meeting       there is something important to write down.

A．as if B．so that     C．in order    D．in case

17、A _____ will be offered for information leading to the arrest of the bank robber.

A. reward       B. award       C. prize       D. profit

16、With the weather worsening，they _______ the voyage from London to Australia．

A. called in     B. called off       C. called out     D. called for

15、This problem may lead to more serious ones if       unsolved．

A．making         B．left          C. remained        D．keeping

14、---What were you doing when I phoned you last night？

---I _______ my painting and was starting to take a bath．

A. have already finished                B. was finishing

C. had just finished                    D. was going to finish

13、—How unhappy your roommate looks!

—Yes, but he's not willing to tell me what it is _______ is troubling him.?

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

12、      he met with the difficulty did he realize the importance of our help．

A．Even though      B．Never until      C．Only before        D．Ever since

11、It’s a little surprising that a house made of wood or bamboo may stay up in an earthquake while ______ made of steel and concrete may fall down.

A. one       B. that        C. it         D. what