A total of 774 doctorates in mathematics were granted to United States citizens by American universities in the 1972～1973 school year, and W of these doctorates were granted to women. The total of such doctorates in the 1986～1987 school year was 362, and ω of these were granted to women. If the number of doctorates in mathematics granted to female citizens of the United States by American universities decreased from the 1972～1973 school year to the 1986～1987 school year, was the decrease less than 10 percent ？（）
(1)
(2)W=ω+5
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．
参考答案：C
解析：
该题也即问[*]是否小于10%。(1)不充分，因为(1)中未涉及ω的值，所以无法判断上面的算式是否小于10%，(2)也不充分，因为由(2)中能得到W-ω=5，而得不到[*]的值，所以也无法判断是否小于10%；(1)+(2)充分：[*]，因此[*]的值必然小于10%。