阅读《白杨礼赞》选段。

　　白杨树实在是不平凡的，我赞美白杨树!

　　汽车在望不到边际的高原上奔驰，扑入你的视野的，是黄绿错综的一条大毡子。黄的是土，未开垦的荒地，几十万年前由伟大的自然力堆积成功的黄土高原的外壳;绿的呢，是人类劳力战胜自然的成果，是麦田。和风吹送，翻起了一轮一轮的绿波，--这时你会真心佩服昔人所造的两个字“麦浪”，若不是妙手偶得，便确是经过锤炼的语言的精华。黄与绿主宰着，无边无垠，坦荡如砥，这时如果不是宛若并肩的远山的连峰提醒了你(这些山峰凭你的肉眼来判断，就知道是在你脚底下的)，你会忘记了汽车是在高原上行驶。这时你涌起来的感想也许是“雄壮”，也许是“伟大”，诸如此类的形容词;然而同时你的眼睛也许觉得有点倦怠，你对当前的“雄壮”或“伟大”闭了眼，而另一种的味儿在你心头潜滋暗长了--“单调”。可不是?单调，有一点儿吧?点击进入 初中学习小组

然而刹那间，要是你猛抬眼看见了前面远远有一排--不，或者只是三五株，一株，傲然地耸立，像哨兵似的树木的话，那你的恹恹欲睡的情绪又将如何?我那时是惊奇地叫了一声的。

那就是白杨树，西北极普通的一种树，然而实在是不平凡的一种树。

进行有性生殖时，亲子代之间传递遗传物质的“桥梁”是（　　）

    On Sunday 23 April, more than 30, 000 people participated in the 2017 London Marathon, running 26.2 miles (42.2 kilometers) around the city centre.

    The London Marathon has taken place every year since 1981. At the first one just6,225 people completed the course, and since then it has grown into one of the biggest sporting events in the world. It is one of the “World Marathon Majors”, which is a competition made up of six global marathon events. The overall male and female winners receive $ 1 million in prize money between them. There are eleven people who have run every London Marathon since it began—they call themselves the “Ever Presents”.

    This year, the winners of the London Marathon were surprisingly both from Kenya— Daniel Wanjiru, who finished in 2 hours and 5 minutes, and Mary Keitany, whose time was 2 hours and 17 minutes.

    However, most marathon runners are not professional athletes. They are amateurs who have trained for months to raise money for charity or just as a personal challenge. For example, Tom Harrison took three days just to reach the run's halfway point, as he is crawling the course on his hands and knees dressed as a gorilla(大猩猩), trying to raise money and attention for the charity “The Gorilla Organization”.

    Matthew Rees was another runner to encourage people, as he stopped just before the finish line to help David Wyeth run the last 200m. They did not know each other before, but Matthew saw that David was exhausted and possibly close to collapsing, and wanted to help him finish.

    Every year there are lots of touching stories like this from the London Marathon, and it is a huge achievement even to run the 26.2 miles!