16. ______D__ it is very late now, the students are still working in the   lab.

A) As

B) When

C) If

D) Although

17. In the world no country has exactly the same folk music ___B_____ that of   any other countries.

A) with

B) as

C) to

D) like

18. He used to ____D____ the first to arrive and the last to leave.

A) is

B) was

C) being

D) be

19. The patients will have to wait all day ___C_____ the doctor works   faster.

A) if

B) whether

C) unless

D) that

20. The new model costs twice ___B_____ last year’s.

A) more than

B) as much as

C) as many as

D) than