题干

为增加农民收入,加速社会主义新农村建设,某市许多乡镇大力发展养蚕业,下较为蚕的生殖、发育过程,请根据图回答:

(1)蚕的生殖方式属于____ 生殖,产生的后代与亲代相似,这种现象,在生物学上称为____ 。
(2)养蚕是为了获取蚕丝,要使蚕丝产量提高,应设法延长蚕发育的____ 期。
(3)图中亲代蚕蛾产生的后代中,有的蚕蛾产的卵是圆形的,有的是纺锤形的,这 种现象在生物学上称为____ 。

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有性,遗传,幼虫,变异

同类题2

I was just outof college, only three days into a graduate (研究生)year in England,and I was pulling a heavy bag and suitcase(箱子)through the London Underground. I was also crying out of control.

   The day before yesterday, my uncle told me never to speak to him, his wife, or my two cousins again. Earlier,  I made a joke. I didn't mean to hurt my aunt's feelings, but it did.I spent the evening in an ugly blue telephone booth (电话亭). crying as I spoke to a family friend who lived in England.

   When I left the phone booth, I went back to a silent house with three closed bedroom doors. In the morning, I heard everyone get up and leave for work and school. I wrote a note to say sorry and pulled my bags to the train station. When I got into London, I had to take the underground to Angel Station to get to my family friend's house.

    I was familiar with the underground, but at the time, it was just endless white tiles(瓷砖).Coming to England seemed like a bad decision. Crying yet again, I tried to lift my suitcase up the stairs.

   When I was trying hard to walk forward, there were hands. Each time I faced another group of steps,a hand would lift the suitcase. At the top of the steps, the hand would let go, and I'd pull the suitcase to the next group. And just as I wanted to try again,another hand would appear.

   It happenedseveral times. I never looked up, because I couldn't stop crying.Each hand looked different, and many different people helped me, without asking or saying anything. I couldn't look up. I wasn't able to say thank you.

   I went on to have anamazing year studying in England, but that was the last time I saw or spoke to any of my uncle's family. Yet when I think about that terrible loss in 2008, I remember those strangers' hands. They were there when I needed them, and even now, they help me out of the sadness of that memory. I think of them as I ride the underground in Washington D. C. today, and I watch the citizens and tourists to offer hands at any time.