听第10段材料，回答第17至第20四个小题．现在你有20秒钟的时间阅读下面四个小题．
17．When will the exam end？

C

C

A．At 9：00am．B．At 10：00am．C．At 11：00am．
18．Why isn't Mr．Green here？

A

A

A．Because he has gone to America．B．Because he's ill．C．Because he has gone to England．
19．Can the students guess in the exam according to the passage？

A

A

A．Yes，they can．B．No，they can't．C．We don't know．
20．Which of the following is true？

C

C

A．If there is a difficult question in the exam，please stop and think it for a long time．
B．Try to leave the questions unanswered when you finish the test．
C．Relax yourselves before you answer the question．