1. 1/3,4/7 ,7/11 ,2/3 ,13/19 ,( ) A.16/21 B.16/23 C.18/21 D.17/21
2.
3.
4. 1,3/8,1/5,1/8,3/35,( ) A.1/12 B.1/16 C.1/18 D.1/24
5.
答案与解析: 1.答案:B 解析:
2.答案:A 解析:
3.答案:B 解析:
4.答案:B 解析:
5.答案:C 解析:
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