III. Choose the correct answer
1. The problem is ............. difficult for us to solve.
A. so                              B. such                   C. too                     D. enough
2. The calculations are________complicated that they cannot be done without a computer.
A. so                              B. such                   C. too                     D. more
3. They can’t work. They are too tired.
 A. When they are too tired, they can work.   
 B. Because they can’t work, they’re too tired.
 C. They are tired but they think they can work.
 D. They are so tired that they cannot work.
4. The more waste paper we recycle, _______.
A. the more trees we preserve                       B. the many trees we preserve
C. the best trees we preserve                         D. the less trees we preserve
5. The ________ have a very hard life. They cannot live permanently in one place.
A.  farmers                     B. nomads              C. workers             D. villagers
6. The streets in cities are ……….. than those in the countryside.
A. crowded                    B. more crowded    C. crowdeder          D. less crowded
7. Ethnic people in the mountainous regions live …………. than people in the city.
A. more simple              B. more simply            C. simpler            D. simplier