题目

阅读短文，从各题所给的四个选项中，选出最佳答案。 Cars are lots of fun, but they could also be dangerous. We have to be careful when we drive them or ride in them. It's always a good idea to put on your seat belt when you're in a car. Why? Think about this example: You put an egg on a skateboard and give it a push. If the skateboard hits a stone, it will stop, but the egg won't. It will fly through the air, hit the ground and break. Now, think what would happen if you tied the egg to the skateboard. When the skateboard hits a stone, the egg won't go flying; it wi 读右侧我国西部雪线高度分布图，回答下列问题。    （1）河流①流域内的主要特色农业（种植业）类型是什么？试分析其形成原因。    （2）河流②流域内种植业区存在的主要生态环境问题是什么？有何相应的防治措施？（4分）