题干

在平面上,我们如果用一条直线去截正方形的一个角,那么截下的一个直角三角形,按图所标边长,由勾股定理有 c2=a2+b2 ,设想正方形换成正方体,把截线换成如图的截面,这时从正方体上截下三条侧棱两两垂直的三棱锥O-LMN,如果用 S1,S2,S2 表示三个侧面面积,S4表示截面面积,那么你类比得到的结论是(   )

A:S4=S1+S2+S2

B:S42=S12+S22+S32

C:S43=S13+S23+S33

D:S44=S14+S24+S34

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B

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    Cleverness is a gift while kindness is a choice.Gifts are easy—they're given after all.Choice can be hard.

    I got the idea to start Amazon 16 years ago.I came across the fact that the Internet usage was growing at 2300 percent per year.I'd never seen or heard of anything that grew that fast,and the idea of building all online bookstore with millions of titles was very exciting to me. I had just turned 30 years old,and I'd been married for a year.I told my wife MacKenzie that I wanted to quit my job and go to do this crazy thing that probably wouldn't work since most start-ups don't and I wasn't sure what to expect.MacKenzie told me I should go for it.As a young boy,I'd been a garage inventor.I'd always wanted to be all inventor,and she wanted me to follow my passion.

    I was working at a financial firm in New York City with a bunch of very smart people and I had a brilliant boss that I much admired.I went to my boss and told him I wanted to start a company selling books on the Internet.He took me on a long walk in Central Park,listened carefully to me,and finally said,“That sounds like a really good idea,but it would be an even better idea for someone who didn't already have a good job.”That 1ogic made some sense to me,and he convinced me to think about it for 48 hours before making a final decision.Seen in that light,it really was a difficult choice,but finally,I decided I had to give it a shot.I didn't think I'd regret trying and failing.And I suspected I would always be haunted by a decision to not try at all.

    After much consideration ,I took the less safe path to follow my passion ,and I'm proud of that choice.For all of us,in the end,we are our choice.