1 . 要在发展和保护文化遗产之间找到平衡，是一个很大的挑战。
It’s a big__________to find and keep the right___________ between the progress and the protection of cultural relics.

2 . When you learn to ride a bicycle, you must learn to keep your b________.

3 . His wife’s death was a great b______ (打击)to him.

4 . Exercise is extremely b_____ (有益的)to health.

5 . Illegal hunting will put those rare animals in danger and break the b_________ of ecosystem.

6 . Our   __________（小册子）is printed on environmentally-friendly paper. （根据汉语提示单词拼写）

7 . Great pity! His illness is ________ the treatment available so far.

A．within

B．above

C．about

D．beyond

8 . Scientists believe that it might be several years ______ the medicine can be used on human beings.

A．since

B．when

C．before

D．until