26.設(shè)1≤a≤40, 化成循環(huán)小數(shù)其循環(huán)節(jié)長(zhǎng)度是（　　�。�
A.40                                                         B.8

C.10                                                         D.5

27.51000被17除的余數(shù)是（　　�。�
A.16                                                         B.13

C.15                                                         D.8

28.下列數(shù)中有可能是3個(gè)連續(xù)排列的奇數(shù)之和的數(shù)是（　　�。�
A. 15                                                        B.14

C.13                                                         D.12

29.3407的個(gè)位數(shù)字是（　　�。�
A.1                                                           B.3

C.7                                                           D.9

30.方程 的正整數(shù)解有______組。（　　　）
A.3                                                           B.4

C.5                                                           D.6