题干

如图所示,汽车前灯反光镜与轴截面的交线是抛物线的一部分,灯口所在的圆面与反光镜的轴垂直,灯泡位于抛物线的焦点处.已知灯口的直径是24cm,灯深10cm,那么灯泡与反光镜的顶点(即截得抛物线的顶点)距离为(  )

A:10cm

B:7.2cm 

C:3.6cm

D:2.4cm

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答案(点此获取答案解析)

C

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    When I was going home to India last year, I called up my mother to ask if she wanted anything from China.

    When India had not opened up its markets to the world, I carried suitcase loads of dark glasses and jeans. Thankfully, we can get all these anywhere in India now.

    Still, her answer surprised me, “Green tea.”

    As long as I can remember she didn't even drink Indian tea.

    I dutifully bought a big packet of Longjing and headed home to hear the story. My mother and her brother, both regular newspaper readers, believed that Chinese green tea was the wonder drug for all illnesses.

    At the turn of the century,China was not really familiar to the average Indians. It was a strange country.

    How things change! And how soon!

    Now every town of any size seems to have a “China Market”. And everyone is talking about China.

    The government of India has planned to send a team to China to see how things are done. A minister once said that India must open the doors for more foreign investments(投资) and such a step would “work wonders as it did for China”.

    But it's a two way street. I just heard about a thousand Shenzhen office workers who have gone to Bangalore to train in software. Meanwhile, all the Indian IT majors are setting up a strong presence in China.

    No wonder that trade, which was only in the millions just ten years ago,was expected to hit about $15 billion for last year and $20 billion by 2008, a goal set by both governments.

    No wonder,my colleague wrote some weeks ago about this being the Sino-Indian(中印) century as the two countries started on January 1 the Sino-Indian Friendship Year.

    But what is still a wonder to me is my mother drinking Chinese tea.