根据短文内容，选择正确答案。

    These days, more and more people begin to pay more attention to their health. They want to take up different kinds of sports to keep healthy. What sports should they do then?

    Tennis

    Thomas opened up a tennis room recently. To his surprise, there were much more people than he expected(预想) coming on the first day. Because no more room was available(可利用的), he had to rent(租借) another bigger room from his neighbour, but it still couldn't meet the need. "I am pleased to see so many people like playing tennis. It is a very good sport for health," said Thomas.

    Football

    Donna works in a bookstore. She often goes to play football in the middle school near the bookstore. "Although the students are having their summer holidays, to my surprise, the playground is crowded with people," said Donna.   

    Of course, there are some other sports that people can do to keep healthy. But it's certain(确定的) that people who often exercise can work better.

植物种子萌发的外部环境条件中，不一定需要的条件是（   ）

下表是我国第五次人口普查时“江苏省某市迁入人口年龄及性别统计表”．据此回答下题：