Why did Sturgeon's electromagnet could support nine pounds of iron?

Most of us，when we reached our teens，started looking forward to the day when we would occupy places of our own，far from the confines of our families. We saw this moving away as a chance to strike out on our own，to grow，to spread out wings and experience freedom. At the same time，we regarded this independence as temporary-the thing to do until we found the perfect mate and married. Over the years，many millions of people have made this passage from one family to another，with just a brief，often nervous interval of independence in between. But recently，more and more people have begun to challenge the concept that living together is better than living alone. Being single is now accepted as an alternative lifestyle-one that is natural，rewarding，and complete. In fact，being single has become almost fashionable.

它能经受时间的考验。

我们系的每个学生都喜欢课外活动。

科学家们将必须提出增加世界粮食供应的新方法。

格林先生退休后，由他的儿子接管他的生意。

不论她如何说，我也不相信这个消息。

Animal research is irrelevant to our health and it can often produce______(mislead)results.

______(salary)people who earn more than a few thousand dollars must pay a certain percentage of their salaries.

Facts are terrible things if______(leave)spreading and unexamined.

As with anything______(carry)to excess，daydreaming can be harmful.