单选题
Committee X and committee Y, which have no common members, will combine to form Committee Z. Does Committee X have more members than Committee Y?
(1)The average (arithmetic mean) age of the members of Committee X is 25.7 years and the average age of the members of Committee Y is 29.3 years.
(2)The average (arithmetic mean) age of the members of Committee Z will be 26.6 years.
(A) 条件(1)充分，但条件(2)不充分．
(B) 条件(2)充分，但条件(1)不充分．
(C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分．
(D) 条件(1)充分，条件(2)也充分．
(E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．
(1)The average (arithmetic mean) age of the members of Committee X is 25.7 years and the average age of the members of Committee Y is 29.3 years.
(2)The average (arithmetic mean) age of the members of Committee Z will be 26.6 years.
(A) 条件(1)充分，但条件(2)不充分．
(B) 条件(2)充分，但条件(1)不充分．
(C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分．
(D) 条件(1)充分，条件(2)也充分．
(E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．
【正确答案】
C
【答案解析】[解析] (1)不充分，因为(1)只是给出了两个委员会成员的各自平均年龄，而没有给出年龄与成员数目之间的关系，所以无法判断两个委员会的成员的多少；(2)同理不能说明哪一个委员会的成员多；(1)+(2)充分，设X委员会的人数为m，Y委员会的人数为n，则Z委员会的人数为m+n，根据题意可得：
