题干

关于基因显、隐性的说法,正确的是( )

A:成对的基因一定有显性、隐性之分

B:隐性基因控制的性状是不能表现出来的

C:一对显性和隐性基因位于一条染色体

D:一对基因都是隐性基因时表现隐性特征

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D

同类题3

阅读理解

    Animals, including insects, do not have a language like ours. They do not talk to each other in words and sentences. But if we watch them, we can see that they do have ways of communicating with each other.

    Can you see the rabbits' tail? When rabbits see this white tail moving up and down, they run too. The rabbit has reminded them of potential dangers without making a sound. It has given them a signal.

    Many other animals use this kind of language. When a cobra (眼镜蛇) is angry, it raises its hood (兜帽) and makes itself look fierce. This warns other animals. When a bee has found some food, it goes back to its home. It cannot tell the other bees where the food is by speaking to them, but it does a little dance in the air. This tells the bees where the food is.

    Some animals say things by making sound. A dog barks, for example, when a stranger comes near. A cat purrs (猫的呜呜声) when pleased. Some birds make several different sounds, each with its own meaning. Sometimes we human beings speak in the same way. We make sounds like “Oh” or “Ah!” when we are frightened or pleased or when we drop something on our toes.

    But we have something that no animals have — a large number of words which have the meanings of things, actions, feeling or ideas. We are able to give each other all kinds of different information in words and sentences, which no other animals can do. No other animals have so wonderful a language as we have.