题干

已知人的有耳垂对无耳垂(a)为显性。某家系三代6人的耳垂遗传情况如下表。下列判断正确的是( )

祖父

祖母

儿子

儿媳

孙子

孙女

有耳垂

有耳垂

有耳垂

有耳垂

无耳垂

无耳垂


A:儿子、儿媳的基因组成都为AA​

B:前两代入耳垂的基因组成不可能完全相同

C:祖父和祖母耳垂的基因组成可能相同也可能不同

D:如儿子和儿媳生育第三个孩子,则该孩子有耳垂和无耳垂的机会均等

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答案(点此获取答案解析)

C

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阅读理解American Country Music
    Over the past twenty years, American country music has become more and more popular. Song writers are no longer writing about the modern values of the USA—money, success or expensive things to buy. Instead they are writing once more about things that are common for everyone: feeling alone in the modern world, the value of having good friends and so on.
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    Then in the 1960s, song writers turned to other subjects. During these years many young students were angry with society, so songs were often full of anger. Political leaders were not well thought of and those songs often made fun of them.
    Today country music has returned. It has become big business and brings in between 200 and 400 million dollars a year. Once, the home of American country music was Nashville, Tennessee. Now, however, the music has reached all parts of the States, from Los Angeles in the west to New York in the east. Singers do not just come from the States but from all over the world.  There are many famous singers from Britain, Canada and Australia. A lot of them appear on television too.
    The first country singers sang while playing the guitar. It was easy for them to carry a guitar on their travels. Now, however, a lot of electrical equipment is needed for large theatres.
    Country music today remains much the same as before. One subject to which country music often returns is “the good old days”. In “the good old days” people thought well of each other. People loved life in the open air. They believed that the best things in life were free: sunshine, laughing, walks in the beauty of the country, friends and music.