1.During this time the selling price, and so profits, will go up and down depending on world demand.

2.Many of us believe that a person's mind becomes less active as he grows older.

3.This means that it took them longer to accomplish mental tasks than it used to.

4.For example, the older person perhaps had trouble hearing, or poor vision, or inattention, or was trying to learn the new thing at too fast a pace.

5.Not only was the shop a center of buying and selling, but also a social meeting place.

6.He will have to give advice and make decisions as problems arise, and he must know how to get his huge staff to work efficiently with their respective responsibilities.

7.Numerous studies have now shown that the overwhelming majority of colds are "caught" by hand contact.

答案：

1.在此期间，煤炭的销售价格及其利润会随着国际市场的需求变化而上下波动。

2.我们很多人都认为，一个人智力会因衰老而变得迟钝。

3.这意味着他们完成智力活动所需的时间比过去长。

4.例如，老年人也许听力差，眼神不好，注意力不集中，或者想尽快地学会做某一件事情。

5.过去商店不仅仅是一个买卖东西的地方，而且是一个社交场合。

6.他必须为手下员工出主意，问题出现之后要做决断，他还必须清楚如何使自己庞大的员工队伍各司其职，高效工作。

7.许多研究表明，绝大多数的感冒是由于手的接触而感染的。