A：转基因生物不会对生物多样性构成威胁，也不会影响生态系统的稳定性
B：应该严格地选择转基因植物的目的，以避免产生对人类有害的物质
C：一旦发现转基因生物出现了安全性问题，应该马上停止实验，并销毁重组生物
D：外源基因插入宿主基因组的部位往往是随机的，有可能会出现意想不到的后果
冬季，我国北方的哈尔滨白雪皑皑，而南方的海南岛则花果飘香，气候宜人。造成这种差异的主要原因（ ）
It is March 12th. It's Tree Planting Day. There are many people on the hills. They're planting trees. People plant many trees today. Plants are important to us. They can make food from the air, water and sunlight. But animals and people can't do so. Animals and people can get food from plants. Without plants, life will not go on, Plants make the air clean. They can keep water from flowing away(流失). They can stop wind from blowing up sand and earth. But in some places people are cutting down too many trees. This brings about floods and sandstorm. Now more and more people know that plants are important. They will plant more trees and grow more plants. They will try to protect the trees.
