1 . 海洋不仅给我们提供了充足的食物，而且它还保持了自然的平衡。
Not only does the ocean offer us sufficient food, but also it ________.

5 . 对露西来说保持工作和家庭生活的平衡是件难事, 所以她只好向她妈妈求助。(it作形式主语)
________________ her work and family life, so she has to turn to her mother for help.

6 . 解决这个烦人问题的方法是好好平衡工作和休息。

__________ working out this annoying problem is to __________ well.

7 . When he first learned to skate, he didn’t know how to ________ and ________ constantly. But now he has learned to ________ while skating.
最初学习滑冰时，他不知道如何使自己保持平衡，经常失去平衡。可是，现在他已经学会了滑冰时使自己保持平衡。

9 . 如何平衡日益发展的心理需求，也是个颇让人头疼好的大问题。
It can be a big headache to ________ your ________ ________ needs too.

10 . Many methods have been tried to ________________________________.
为了保持自然的平衡，许多方法已经被尝试。