问题
单项选择题
DNA是绝大多数生物的遗传物质，以下生物非以DNA为遗传物质的是（）
A.大肠杆菌
B.T2噬菌体
C.烟草花叶病毒
D.酵母菌
答案
参考答案：C
解析：大肠杆菌是原核细胞，酵母菌是真核细胞，遗传物质都是DNA；T2噬菌体是病毒，遗传物质是DNA；烟草花叶病毒也是病毒，遗传物质是RNA；答案选C。
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DNA是绝大多数生物的遗传物质，以下生物非以DNA为遗传物质的是（）
A.大肠杆菌
B.T2噬菌体
C.烟草花叶病毒
D.酵母菌
参考答案：C
解析：大肠杆菌是原核细胞，酵母菌是真核细胞，遗传物质都是DNA；T2噬菌体是病毒，遗传物质是DNA；烟草花叶病毒也是病毒，遗传物质是RNA；答案选C。
Big schoolbags have been a big problem for students for a long time. Maybe your schoolbag is too 1 to carry, and it troubles you a lot 2 you want to find out a book to read. Now e-textbooks will 3 you. It is said that many Chinese middle schools are going to use e-textbooks. An e-textbook, in fact, is a small 4 for students. It is much 5 than a usual schoolbag and easy to carry. Though it is as small as a book, it can 6 everything for study. The students can read the text page by page on the 7 ，take notes 8 the pointer (屏写笔)，or even “hand in” their 9 to their teachers by sending e-mails. All they have to do is to press a button (按开关). Some people say e-textbooks are good, but some say they may be 10 for the students’ eyes. What do you think of it?
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