21. The air in the city is badly polluted, ____ give up the idea of having cars, ____ have a cleaner atmosphere.
A. Only will when people; shall we B. when only people; we will
C. Only when people; can we D. When people only; we will
22. The film Avtar was made with the latest technology. It is really___ to see it and you will know what 3D is.
A. worth B. worthwhile C. worthy D. valuable
23. The old man has three sons, _______ lives with him.
A. none of them B. some of them C. none of whom D. some of whom
