某兴趣小组在探究环境对生物影响的实验中，选择鼠妇做实验。取一个厚实的纸盒，一侧盖上纸板（阴暗），一侧盖上玻璃板（明亮），在两侧的中央各放入5只鼠妇，静置2分钟后，每隔1分钟记录一次明亮和阴暗处的鼠妇数目写下表统计10此填写下表：

（1）实验的变量是________________________。
（2）一侧盖上纸板，另一侧盖上玻璃板，其作用是________________。
（3）要用10只鼠妇做实验的原因是__________________________________。
（4）根据表中数据，你得出结论：__________________________________。
（5）该兴趣小组还可以探究非生物因素中的_____________对鼠妇生活的影响。

阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项。

    Many facts suggest that children are overweight (超重的) and the situation is getting worse, according to the doctors. I feel there are a number of reasons for this.

    Some people blame the fact that we are surrounded by shops selling unhealthy, fatty foods, such as fried chicken and ice cream, at low prices. This has turned out a whole generation of grown-ups who seldom cook a meal for themselves. If there were fewer of these restaurants, then probably children would buy less take-away food.

    There is another argument that blames parents for allowing their children to become overweight. I agree with this, because good eating habits begin early in life, long before children start to visit fast food shops. If children are given fried chicken and chocolate rather than healthy food, or are always allowed to choose what they eat, they will go for sweet and salty foods every time, and this will carry on throughout their lives.

    There is a third reason for this situation. Children these days take very little exercise. They do not walk to school. When they get home, they sit in front of the television or their computers and play computer games. Not only is this an unhealthy pastime (消遣), it also gives them time to eat more unhealthy food. What they need is to go outside and play active games or sports.

    The above are the main reasons for this problem, and therefore we have to encourage young people to be more active, as well as steering them away from fast food shops and bad eating habits.

我国水旱灾害比较频繁的最主要原因是（   ）