人工选择所以能培育出新品种来，自然选择所以能形成新的物种，它们共同的基础是_刷题宝

题干

人工选择所以能培育出新品种来，自然选择所以能形成新的物种，它们共同的基础是（　　）

A：生物都有很强的繁殖能力

B：生物的遗传和变异是普遍存在的

C：生物都在进行生存竞争

D：人和自然的选择力量

上一题下一题 0.0难度选择题更新时间:2018-07-28 02:01:31

答案(点此获取答案解析）

B

同类题1

阅读理解

It is Sunday today. It is my grandma's birthday. Father, mother and I go to visit her.

She lives with my uncle. In the morning we buy a birthday cake and some fruits and go to her house at ten o'clock.

We spend about half an hour getting there. My grandma and uncle are very glad to see us. We give the presents to grandma and say“Happ y birthday to you! ”She is very happy. Then we sit down to talk. My uncle can cook.

The meal is very nice. We all like it very much. After lunch, I play with my uncle. At four o'clock, we say goodbye and go home.

同类题2

---Is there anything wrong, Bob? You look sad．
---Oh, nothing much．In fact, I ____ of my friends back home．

同类题3

已知函f（x）=

{\begin{matrix} \log_{3} x, x > 0 \\ 2^{x}, x \leq 0 \end{matrix}

\frac{1}{9}

同类题4

20世纪70年代人们吃的是“温饱”；80年代吃的是“口味”；90年代吃的是“花样”；现在，人们吃的是“健康”。不同的时代，消费的内容发生了巨大的变化，这主要说明了（）
①家庭消费从低级逐步向高级发展　②我国居民的生活水平和恩格尔系数不断提高　
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同类题5

The old house we paid a visit _____ at the top of the hill.

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