人的性别决定与性染色体有关，男性的表示方式是和女性的分别表示方式是（ ）
A．Y，X
B．XX，XX
C．XY，XX
D．X，Y
性染色体是与决定性别有关的染色体，人类的性染色体是X和Y染色体，X染色体较大，Y染色体较小；人的体细胞内的23对染色体，有一对染色体与人的性别有关，叫做性染色体．常染色体就是对性别决定不起直接作用，除了性染色体外的所有染色体．例如，人类有22对常染色体，1对性染色体．人类正常染色体为46条（23对），其中22对称为常染色体，男女都一样；第23对称为性染色体，人的性别主要是由性染色体决定的，男性体细胞中的一对性染色体组成是XY，女性体细胞中的一对性染色体组成是XX．从性染色体的来源看，是生男还是生女，主要决定于从父亲那里得到的染色体是X还是Y．是X就是女儿，是Y就是儿子．
故选：C
请认真阅读下列短文，并根据所读内容在文章后表格中的空格里填入一个最恰当的单词。 注意：请将答案写在答题卡上相应题号的横线上。每个空格只填1个单词。 Color use in nature Nature is very colorful, full of different hues（色调）that delight the eye. What makes these colors and why do they exist? Causes of Colors in Nature Colors in nature are formed in two ways. Pigments, like the melanin in skin and many animal furs, produce most blacks, browns, reds and yellows. Most plants are green due to chlorophyll（叶绿素）. Other colors are caused by structure, like many greens, blues, and whites. Blue bird’s feathers actually contain black pigment, but their structure causes them to appear blue. The scattering of light by tiny dust particles in the air, viewed against the black background of space, makes the sky look blue too. Color Use in Plants Color has a great effect on the survival of plants and animals. Flowers have bright hues and patterns to attract insects. These insects move from one flower to another, making sure seeds are produced. Bees can see colors we cannot, i.e. ultraviolet, and follow these patterns of stripes or dots to the inside of the flower. Not only flowers but also fruits use color for the good of the plant. An unripe fruit mixes in with the leaves, but ripe berries contrast, becoming more appealing to the creatures who eat them. Birds are especially drawn to red fruit, and in turn help the plant by broadcasting its seeds. Camouflage（伪装）in Nature Many colors and patterns camouflage animals who want to avoid enemies. Some animals have damaging shapes to break up their outline, so an enemy will not recognize them. The eye, a very recognizable animal characteristic, is often disguised by a black stripe or patch. Light color below makes up for the shadow on the underside of many fish, amphibians and mammals. Some animals even change colors to better camouflage themselves, seasonally like the snowshoe hare. Warning Coloration and Mimicry（动态伪装） Warning colors make an animal more visible rather than hidden. These usually indicate a negative aspect of the animal, like the bad taste of a monarch butterfly, smelly smell or painful bite of a bee. Usually black and a contrasting color (white, yellow, orange or red) form a striking pattern in these creatures, and frighten their enemies away. Nature is tricky, though, and sometimes harmless creatures pretend the patterns of harmful ones to scare off animals living on meat too. Social Coloration in Nature Sometimes coloration is important socially. Male birds, typically more colorful, defend their territories and attract females. Eggs may use color and pattern to remain hidden. When they hatch, parents feed the nestlings when they see the bright pattern in their gaping mouths. Taking a closer look at nature throws light on how color is used in marvelous ways!
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