题干

如图为利用纯合高秆(D)抗病(E)水稻和纯合矮秆(d)易染病(e)水稻快速培育优良品种纯合矮秆抗病水稻(ddEE)的示意图,下列有关叙述正确的是(    )

A:①过程的主要目的是让控制不同优良性状的基因组合到一起

B:②过程中非同源染色体的自由组合发生在减数第一次分裂前期

C:③过程获得的植株为单倍体,单倍体就是指体细胞中含有一个染色体组的个体

D:获得无子番茄所用原理与④过程相同

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A

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    When I was a little kid, one of my favorite things to do was going to the zoo. I have recently heard that there are debates as to whether elephants should live in zoos or should they wander around free. My position is that elephants should live in zoos for people to see.

    Many experts say that elephants have a good life living in zoos. There are 78 zoos that exhibit elephants. Most zoos are taking the necessary steps to make living conditions better for the elephants. They are doing things such as replacing hard floors with sand or dirt. This makes it easier for them to wander around. Zoos are also expanding their elephant house to give the large animals more room to go around.

    Zoos also protect endangered species. According to the World Wildlife Fund, in 2014 the total population of African elephants was around 700,000, and the Asian elephant population was around 32,000. The Asian elephants are on a path to dying out. Without zoos, they all are likely to disappear within our lifetime. The National Zoo plans to spend millions of dollars on a new Asian elephant habitat. That way, they can start their own group if the Asian elephants are gone.

    There are people who want zoos to empty all of their elephant displays. If they decide to do so, it would take the chance to see elephants up close away from people. That could change the public's favorable opinion of elephants. National Zoo director John Berry says that allowing visitors to experience the elephants up close encourages people to care about endangered species.  During one of my visits to the zoo, it was a very hot day. I was sweating a lot. Big Ben, the largest elephant on display, walked up to me and gently squirted(喷) my face with water from his trunk. Everyone was amazed at what he did. That was a very nice thing for Big Ben to do. I am sure that elephants are the nicest animals on earth. I wish all zoos would keep their elephant displays open to the public. I want all my friends to be able to experience what I did with Big Ben.

    I feel zoos should follow all the necessary steps to keep elephants in zoos. I would raise money at my school if I thought it would help to keep elephants in zoos.