If x is a positive integer, is the remainder 0 when (3^x
                + 1)/10?

(1)     x = 3n + 2, where n is a positive integer.

(2)     x > 4

                  

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

没找到讨论。。

答案选E，但我选了A~~

个人认为：x=3n+2,那么3的x次方的末尾为9，3的X次方+1的末尾为0，能被10整除啊。。

谢谢谢谢。。。

3^x  个位呈3，9，7，1循环

只有x=4n+2，n是正整数或0时，3^x  +1才能被10整除