题干

试管婴儿、试管苗和克隆羊是现代生物科技的杰出成果,这些生物学原理及其技术的共同点是(  )

A:均属于无性生殖

B:运用了细胞工程技术

C:均没有发生基因重组

D:体现了高度分化的细胞具有全能性

上一题 下一题 0.0难度 选择题 更新时间:2019-12-15 10:38:51

答案(点此获取答案解析)

B

同类题4

阅读下列短文,从下面每小题的 A、B、C、D 四个选项中选出最佳选项。

B

    Last summer, Mac Hollan, a primary school teacher, was cycling to Alaska with two friends. On the way, his friends had to stop for a bicycle repair, but they encouraged Mac to ride on, and they would catch up with him soon.

    Mac began to cycle alone. A few minutes later, Mac heard quick and loud breathing behind him. "Man, that's a big dog!" he thought. But when he looked to the side, he saw immediately that it wasn't a dog at all, but a wolf, quickly catching up with him.

    Mac's heart jumped. He searched and took out his can of bear spray(防熊喷雾). With one hand on the bars, he fired the spray at the wolf. A bright red cloud enveloped the animal. To Mac's relief(宽慰), it fell back, shaking its head. A minute later, however, it was again by his side. It even attacked the back of Mac's bike, tearing open his tent bag. He fired at the wolf a second time, and again, it fell back, only to quickly restart the chase(追赶).

    Mac was riding hard now. He waved and shouted at passing cars without slowing down.

    At that moment, Paul and Becky were driving their car on their way to Alaska. They found a dog-like animal running alongside a man on a bike. As they got closer, they realized that the "dog" was a wolf. Mac heard a large car behind him. He kept waving and shouting as the wolf was catching up closer. And the car did stop in front of him at the right time.