题干

若一个多边形的每个外角都等于60°,则它的内角和等于(   )

A:180°

B:720°

C:1080°

D:540°

上一题 下一题 0.0难度 选择题 更新时间:2014-04-25 09:01:43

答案(点此获取答案解析)

B

同类题1

阅读理解

    Having three cancer patients in the same household can turn a whole family upside down. Michelle Bruce, her husband, Jeremy, and their son, Holden, all had cancer. The family moved to Michelle's hometown of Franklin, Nebraska six years ago, so her parents could help.

    Doctors found Holden's brain tumor(肿瘤), when he was 12 years old. His family was living in a small town at the time, but there were related doctors in the state. Holden had two operations in Omaha clinic, both of which were tough.

    When Holden's cancer came back again in 2012, nothing could be done. But the family didn't give up. They reached out to Boston Children's Hospital, which has better equipment and doctors with more experience operating on kids. After looking at Holden's records, the doctor sent back her diagnosis: She was confident that she could remove the tumor.

    The family was beyond relieved, until they learned insurance wouldn't cover any of the operation's costs. The operation would cost $39,000 – more than the parents could afford. The family got desperate.

    In a town of just 1,000 people, however, word traveled fast. Within days, a local woman Michelle had never met in person called to say she was planning an event to raise money for Holden. Michelle was touched.

    The event was uplifting. Finally, the town raised $45,000 – enough to cover not just Holden's hospital bills, but for Michelle and Jeremy's trip to Boston with their son. “I just didn't know what to say,” said Michelle. “Nobody could really believe it.”

    Holden's operation went much more smoothly than the first two. He is cancer-free and now is attending Central Community College-Hastings on a full-ride scholarship.

同类题4

阅读下面的文字,回答问题

咖啡“毁”眼

赵尚泉

       ①“美酒加咖啡,我只要喝一杯,想起了过去,又喝了第二杯……”邓丽君甜美的歌声,加深了人们对咖啡的印象,也激发了一些人品尝咖啡的欲望。

       ②咖啡的益处主要是,它能滋养皮肤,有助于消除疲劳,可预防胆结石,具有一定的抗氧化及开胃促食、活血化瘀、息风止痉等作用;此外,咖啡可能还有解酒作用。当然,其害处也不能忽视,就是它会造成人神经过敏,加剧高血压,诱发骨质疏松,饮用过量会有致癌危险,咖啡中所含的物质会让人上瘾……

       ③不管咖啡是功大于过,还是相反,现在科学家又发现了咖啡一大“危害”,那就是:咖啡“毁”眼。

       ④我们知道,青光眼是一种发病迅速、危害性大、随时导致失明的常见疑难眼病。青光眼的起因是眼内压不稳定,出现了间断或持续性升高,其压力水平超过眼球所能耐受的程度后,给眼球各部分组织和视功能带来了损害,造成视神经萎缩、视野缩小、视力减退,甚至引发失明﹣﹣在急性发作期一两天即可完全失明。而新的研究发现,这种带有毁灭性的眼病竟然和咖啡有一定因果关联。

       ⑤为了搞清楚喝咖啡是否影响眼睛,美国一个科研小组曾专门进行了实验,探讨饮用一杯容量为237毫升的咖啡﹣﹣这个非常有限的咖啡饮用量对眼睛的影响。结果表明,适量饮用咖啡对正常人眼睛的不良刺激不明显,但对患有眼部疾病的人,特别是青光眼患者,有轻微的不良影响,但不会造成什么危害。

       ⑥但长期饮用过量的咖啡,会对眼睛有什么影响呢?

       ⑦另外一个美国研究小组则依据1980年到2008年的医学资料分析,对40岁以上、没有青光眼或癌症病史且有眼科检查报告的人群进行了跟踪调查研究。研究人员每4年对他们进行一次问卷调查,以此来评估这些人日常的咖啡因摄入量,并进行多种可能性分析。结果发现,这些原本没有眼病的人当中,有一少部分因过量饮用咖啡,逐渐患上了青光眼。

       ⑧最近,美国一个研究学会又对这个问题进行了研究。研究人员分析了75000多名女性的健康数据,结果显示,重度咖啡饮用量与青光眼的产生有密切的关系,日常饮用量越大,患青光眼的可能性就越高,而且有青光眼家族史者比没有家族史者,患青光眼的可能性高。这表明,基因和咖啡对诱发青光眼都有作用,而过量饮用咖啡会“毁”眼,确实是不争的事实。

       ⑨看来喜好喝咖啡的朋友真的是要谨慎:_________________________________________________。

(选自2014年第3期《大科技﹒科学之谜》,有删改)