题目

分裂期细胞的细胞质中含有一种促进染色质凝集为染色体的物质。将某种动物的分裂中期细胞与G1期（DNA复制前期）细胞融合后，可能出现的情况是  （    ） A．来自G1期细胞的染色质可以复制 B．融合细胞的核DNA含量是G1期细胞的2倍 C．此时融合细胞内基因表达不活跃 D．融合后两细胞仍按各自的细胞周期运转You can’t see any object unless light from that object gets into your eyes．Some of the things you see give off light of their own。The sun，the stars，a lighted lamp are the examples that can be seen by their own light．But most of the things you see are not giving off light of their own．They are just reflecting(反射)light that falls on them from the sun or some other luminous bodies．The moon，for example，doesn’t give off any light of its own．It is not 1uminous．You see it because sunlight falls on it and some of the sunlight reflects on the earth．So moonlight is only second—hand sunlight． When you look at a book，it sends some of the light which fails on it to your eyes，and you see the book．If light could be kept out from where you’re so that there would be no light from the book to reflect．Then you couldn’t see the book even with your eyes wide open．Light travels so fast that the time in which it travels from the book you’re reading to your eyes is as short as if there were no time at time．Light reaches us from the moon，which is about 380，000 kilometres away，in only a little more than a second．1.You can see the book because________．A.your eyes are close to itB.it reflects some of the lightC.it has light of its ownD.it is big enough to be seen2.The Chinese meaning of the world“luminous”is close to_______．A.闪光的B.看不见的C.发光的D.明亮的3.________has light of its own．A.The moonB.The earthC.The sunD.The satellite of Dong Fong Hong4.Light travels about_________kilometers per second．A.300，000B.100，000C.400，000D.190，0005.Which of the following is TRUE?A.All the things you can see give off light．B.Light from the book is much faster than that from the moon．C.The moment you open your eyes，the light from the book travels to your eyes．D.Light travels so fast that there is no time for you to read．