() 3. It is difficult for US climb up the mountain.

   A. very;can’t   B. too;not C. too;to   D. much;to

() 2. He is to go to school.

   A. old enough   B. enough old C. big enough   D. enough big

() 1. He wasn’t with his knife. He cut himself.

   A. careful enough   B. enough careful C. carefully enough   D. enough carefully

8. The car is not cheap enough for me to buy.(改为同义句) 

The car is to buy.

7. The boy is too weak to carry the box.(改为同义句) 

The boy is not carry the box.

6. My grandfather is too old to travel around (改为同义句)

 My grandfather is to travel around.

5. The box isn’t light enough for him to carry.(改为同义句) 

The box is for him carry.

4. My brother was very clever and he could work out the problem.(改为同义句)

 My brother was work out the problem.

3. Mr King is very busy at work. He can’t take a holiday.(改为同义句)

 Mr King is take a holiday.

2. The ice on the lake was very thin and people couldn’t skate on it.(改为同义句)

 The ice on the lake was people skate on it.