16.既約分?jǐn)?shù) 可化為有限小數(shù)，則應(yīng)滿足的條件是（　　�。�
A.b的質(zhì)因數(shù)只可能是2，3                      B.b的質(zhì)因數(shù)只可能是2，5

C.b的質(zhì)因數(shù)只可能是2，3，5                 D.b的質(zhì)因數(shù)只可能是3，7

17.已知m, n, k為整數(shù)，若3|6m+9n+2k，則必有（　　�。�

A.3|m                                                       B.3|n

C.3|k                                                        D.3|m+n

18.若a+b+c是奇數(shù)，下列說法正確的是（　　�。�

A.a, b, c都是奇數(shù)                                     B.a, b, c至少有一個為奇數(shù)

C.a, b, c中至多有一個是奇數(shù)                   D.以上說法都不對

19.下列不定方程無解的是（　　�。�
A.3x+5y=11                                              B.60x+123y=25

C.21x+35y=98                                           D.1402x-1969y=2

20.若9位數(shù) 是3的倍數(shù)，則下列說法正確的是（　　�。�
A.a與b都是3的倍數(shù)                               B.a+b是3的倍數(shù)

C.3|a                                                         D.3|b