题干

马的黑色与棕色是一对相对性状,现有黑色马与棕色马交配的不同组合及结果如下:

①黑×棕→1匹黑  ②黑×黑→2匹黑  ③棕×棕→3匹棕   ④黑×棕→1匹黑+1匹棕

根据上面的结果,下列说法正确的是(    )

A:黑色是显性性状,棕色是隐性性状

B:棕色是显性性状,黑色是隐性性状

C:交配的不同组合中的黑马和棕马肯定都是纯合子

D:无法判断显隐性,也无法判断哪种马是纯合子

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答案(点此获取答案解析)

D

同类题4

先通读下面的短文,然后根据短文内容,在文章后表格的空格内填入一个最恰当的单词。所填单词必须写在答题卡对应题号的横线上。每个空格只能填一个单词。

    Clothing(服装) is a language. We can look at the traditional clothing to know more about culure.

    Africa has a long history and a rich culture, and this is shown in traditional dress. The three colours—red, gold and green, are often used in the clothing. The first colour represents the blood of millions of people who fought for freedom; the second, rich resources of the African earth; and the third, the grassland of home.

    Because clothing has strong social meanings, people are very careful in choosing what to wear. It would be a serious mistake to wear the wrong clothes, or to dress in the wrong way. For example, in Ghana, a woman should wear her waistband (腰带) differently according to the importance of the social event.

    Traditional dress also tells us about everyday life. African designs are famous for loose (宽松的) clothing. The temperature there can be very high during the daytime but very low at night, so it requires that the clothes are comfortable for daily life.

    Today although more and more young people like wearing Western clothes, especially in big cities in Africa, traditional African dress is still quite valuable. This is because it has deep cultural meanings.

Traditional Dress in Africa

Different colours

 The three most ____ colours used in clothing are red, gold and green.

 Different colours ____ for different things: the blood of freedom fighters, resources of the earth and the grassland of home.

Social meanings

 Because clothing has strong social meanings, people have to choose what to wear ____

 Women in Ghana even wear different waistbands according to how important the event is.

Everyday life

 Because the temperature ____ greatly, clothes are usually loose and comfortable.

 Though Western clothes are popular with young people in some areas, traditional clothes are still of great ____