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问题 综合

大气中二氧化碳含量增多导致全球气候变化。已成为全球关注的热点问题。下图为地球热量平衡示意图。读图多项选择。（8分）

（1）二氧化碳含量增多．导致大气对地面保温作用增强。下列数字所示环节与大气保温作用直接相关的有      

A．①    B．②    C．③    D．④

（2）全球气候变化会对粮食生产产生较大影响．其主要原因是        

A．作物的生长发育受到影响         B．旱涝灾害增多

C．某些物种灭绝                  D．土壤肥力下降

答案

（1）AC（2）AB

单项选择题

A


Hello,everyone. Because of the high rate of school violence(力)in some areas, teenagers’ safety becomes a serious problem. We are planning to set up an organization named School Watch to make sure that students have a safe school environment. Please be part of our plan!
What is School Watch
School Watch is a volunteer project in our school. It helps us stop violence and improve the quality of school life. It will keep yourself and your schoolmates safe. The other members of School Watch care for you and your classroom and you do the same for them.
Is it for everyone
Anybody can become a member of School Watch because everyone has something to offer.
What else can it do
School Watch makes it possible for us not only to help each other But also to make friends with each other. Some members may offer to help schoolmates who have problems with their homework.
Who is the Best School Watcher
Our school will look for the Best School Watcher and give him or her lots of prizes. You could be the one !
How do you start
To be part of this plan, the only thing you need to do is to talk to the director of the plan in your grade. If you want to get more information, check the official website at www.schoolwatch.com.

The Best School Watcher will get a lot of prizes from ______ every year.

A．the school

B．the website

C．the organization

D．the society
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选择题
求如图所示的交变电流的有效值，其中每个周期的后半周期的图象为半个周期的正弦曲线（   ）

A．5A

B．5A

C．5/2A

D．/2A
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