题干

如图为某森林生态系统植物分布情况及不同高度高30的光强百分比示意图,据图分析正确的是度(  )

A:单独种植玉米时,因群落具有分层现象所以要合理密植

B:导致植物垂直分层的原因是光照强度,动物的垂直分层受植物的影响

C:图中所有生物构成了生物多样性

D:人类的过量砍伐会使该生态系统的恢复力稳定性下降

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B

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    Social media is one of the fastest growing industries in today's world. A study conducted by the US Pew Research Center showed that 92 percent of teenagers go online daily. The wide spread of social media has changed nearly all parts of teenagers' lives.

    Changing relationships

    High school student Elly Cooper from Illinois said social media often reduces face- to-face communication. “It makes in-person relationships harder because of people's attention given to their phones instead of their boyfriends or girlfriends,” Cooper said.

    Yet, some people believe social media has made it easier to start relationships with anyone from anywhere. Beth Kaplan from Illinois met her long-distance friend through social media. He currently lives in Scotland, but they're still able to frequently communicate with each other. “I can feel close to someone that I'm talking to via FaceTime,” Kaplan said.

    Wanting to be “liked”

    The rise of social media has changed the way teenagers see themselves. The 19- year-old Essena O'Neill announced on the social networking service Instagram that she was quitting social media because it made her unable to stop thinking about appearing perfect online. Negative comments also can do great damage to a teenager's self-esteem. Teenagers who get negative comments can't help but feel hurt.

    Opening new doors

    However, Armin Korsos, a student from Illinois, takes advantage of the comments he receives over social media to improve his videos on the social networking site YouTube. “Social media can help people show themselves and their talents to the world in a way that has never been possible before,” Korsos said.