在自然保护区外围不可划定一定面积的外围保护地带。（）
参考答案：错
Not until his mother came back_______.
A．he began to do his homework
B．had he began to do his homework
C．he had begun to do his homework
D．did he begin to do his homework
Amy is ________. She often tells us some interesting stories (故事). [ ]
A. polite
B. helpful
C. funny
D. happy
