农业科技人员向农民建议：在利用温室生产时，可向温室中施加适量的干冰，这主要是( )
A．CO2可使害虫窒息死亡，从而能有效地防治植物病虫害
B．植物的光合作用需要CO2，使用CO2可促进光合作用
C．CO2可产生温室效应，使温室内的温度稳中有升
D．CO2能灭火，施用CO2可避免火灾的发生
BC
CO2浓度的提高可以促进光合作用；CO2为温室气体，可使室内温度稳中有升。
One day, the father of a very rich family took his son on a trip to the countryside. He wanted to show his son how poor people lived. _____小题1:______.On their returen from their trip, the father asked his son, “How was the trip?” “_______小题2:______.” “Did you see how poor people live?” the father asked. “Oh yeah,” said the son. “So, tell me, what did you learn from the trip?” asked the father. The son answered,“We have one dog and they have four. We have a pool that reaches to the middle of our garden and they have a river that has no end.____ 小题3:_____. We have a small piece of land to live on and they have fields that go beyond our sight. We have servants who serve us, but they serve others. We buy our food, but they grow theirs. We have walls around our garden to protect us, but they have friends to protect them.” The boy's father was speechless. Then his son added, '' ___小题4:________.”
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