题干

如图,在△ABC中,AB=AC,AB的垂直平分线交边AB于D点,交边AC于E点,若△ABC与△EBC的周长分别是40,24,则AB为(   )


A:8

B:12

C:16

D:20

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答案(点此获取答案解析)

C

同类题3

阅读下面材料, 从每题所给的A, B, C, D四个选项中选出最佳选项。

C

    Life is full of surprises and you never know how things will turn out. Sir John Gurdon. Is a good example of this. As a boy, he was told he was hopeless at science and finished bottom of his class. Now, aged 79, the very same Gurdon shared the 2012 Nobel Prize in Medicine with Japanese stem cell (干细胞) researcher Shinya Yamanaka.

    Like so many scientists, Gurdon shows us where the power of curiosity and perseverance (坚持) can lead.

    At the age of 15 in 1948, Gurdon ranked last out of the 250 boys at his high school in biology and every other science subject. Gurdon's high school science teacher even said that his dream of becoming a scientist was quite "ridiculous".

    In spite of his teacher's criticisms, Gurdon followed his curiosity and kept working hard. He went to the laboratory earlier and left later than anyone else. He experienced thousands of failures.

    "I believe that we will, in the end, understand everything about how cells actually work." Gurdon said.

    In 1962, Gurdon took a sell from an adult frog and moved its genetic (基因的) information i nto an egg cell. The egg cell then grown into a clone of the adult frog. This technique later helped to create Dolly the sheep in 1996, the first cloned mammal in the world.

    In 2006, Gurdon's work was developed by Yamanaka to show that a sample (样本) of a person's skin can be used to create stem cells. Using the technique, doctors can repair a patient's heart after a heart attack.

    "Luck prefers the prepared mind." Gurdon told the Nobel Prize organization. "Ninety percent of the time things don't work, but when they do, you have to catch the chance."

同类题5

外交,就是处理国与国之间关系的政治活动。外交活动,既靠外交智慧,更靠国家实力。

材料一:正当人们欢欣鼓舞地迎接20世纪到来之际,清政府却是“带着首都被敌人攻占的耻辱”,收到了一份“西方人送来的令人不堪忍受的礼物”。

材料二:最近中国和印度曾经达成一项协议。在这一协议中,它们规定了指导两国之间关系的某些原则,这些原则是:甲、互相尊重领土主权;乙、互不侵犯;丙、互不干涉内政;丁、平等互利;戊、和平共处。两国总理重申这些原则,并且感到在他们与亚洲以及世界其他国家的关系中也应该适用这些原则。——摘自《中印关于中国西藏地方和印度之间的通商及交通协定》序言

材料三:“我们共产党人从不讳言,我们相信共产主义和认为社会主义制度是好的,但是在这个会议上用不着来宣传个人的思想意识和各国的政治制度。中国代表团是来求同而不是来立异的……”——周恩来

材料四:“(1972年访问中国时)我走完梯级时决心伸出我的手,一边向他(周恩来)走去.当我们的手相握时,一个时代结束了,另一个时代开始了。”——选自《尼克松回忆录》

材料五:“法国常驻联合国代表说:“中国在我们当中就坐了属于她的席位,不公正和荒谬的状态结束了。”

材料六:20世纪80年代以来,随着“一国两制”伟大构想的提出,中国政府于1997年、1999年先后恢复对香港和澳门行使主权。——岳麓版《中国历史》八年级下册