问题
选择题
用显微镜观察紫色洋葱表皮细胞时，一般看不到染色体，这是因为（ ）
A．紫色液泡干扰了观察
B．染色体没有被染色
C．洋葱表皮细胞一般不分裂
D．洋葱表皮细胞无细胞核
答案
因为染色体在细胞有丝分裂时才会出现，平时是以染色质的形式存在，这是一种很细的东西，要电子显微镜 才能看到．洋葱表皮不再有丝分裂，所以看不到．
故选C．
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用显微镜观察紫色洋葱表皮细胞时，一般看不到染色体，这是因为（ ）
A．紫色液泡干扰了观察
B．染色体没有被染色
C．洋葱表皮细胞一般不分裂
D．洋葱表皮细胞无细胞核
因为染色体在细胞有丝分裂时才会出现，平时是以染色质的形式存在，这是一种很细的东西，要电子显微镜 才能看到．洋葱表皮不再有丝分裂，所以看不到．
故选C．
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| My English teacher is Lucy. She comes from England. She is 28 years 1 . She likes Chinese food. 2 favorite food is Chinese Jiaozi. She has a son and 3 boy was born (出生) on May 4th, 2007. My 4 is May 4th, too. It's interesting. Lucy's English classes are very 5 . She likes to play the games 6 the students in class. We all like her. She draws very 7 , and she often draws pictures for us after class. Today is her birthday. We come to her birthday 8 and give her many presents(礼物). She is very 9 . She says China is her second home. She 10 China very much. | ||||
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