根据材料内容，从下面五个选项中选出能填入文中空缺处的最佳选项，使短文意思通顺，内容完整，并将其标号填涂在答题卡的相应位置。
Science and technology are developing quickly. On the one hand they can improve our lives, but on the other hand, they can cause pollution. 小题1:
Air pollution is a serious problem. Factories and heavy traffic give out a lot of smoke and make the air dirty. 小题2:So the government should take action and make everyone keep the air clean.
The main reasons for noise pollution are heavy traffic and road works. 小题3:Therefore, the government should try to make less noise.
Factories put a lot of dirty water and chemicals into the rivers and the sea. They pollute the water. 小题4: And it also can make sea animals sick. So the government should stop factories doing that.
The main reasons for land pollutions are construction and people. Construction makes much waste and people throw away a lot of rubbish every day. 小题5: People should stop throwing away so much rubbish and start using old things again.
