20. It is these poisonous products _______ can cause the symptoms of the flu, such as headache and aching muscles.
A. who B. that C. how D. what
21.It is the ability to do the job _______matters not where you come from or what you are.
A. one B. that C. what D. it
22. It was not until 1920 _____ regular radio broadcasts began.
A. while B. which C. that D. since
23. _____ is a fact that English is being accepted as an international language.
A. There B. This C. That D. It
24. It was only with the help of the local guide ___________.
A. was the mountain climber rescued
B. that the mountain climber was rescued
C. when the mountain climber was rescued
D. then the mountain climber was rescued
25. Who was it _____ put so many large stones on the road?
A. this B. that C. he D. she
26. What a silly mistake it is _____ you’ve made!
A. it B. this C. that D. which
27. It was the boy _____ had been in prison _____ stole the money.
A. who, where B. that, how
C. who, that D. that, which
28. Why was _____ that the old woman was sent to prison?
A. he B. it C. that D. what
29. It was when she was about to go to bed _____ the telephone rang.
A. since B. as C. that D. then
30. It may have been at Christmas _____ John gave Mary a handbag.
A. before B. who C. that D. when