问题
单项选择题
One night 18 percent of the female officers on a police force were on duty. If 180 officers were on duty that night and half of these were female officers, how many female officers were on the police force ？（）
A.90
B.180
C.270
D.500
E.1，000
答案
参考答案：D
解析：
那天夜里值夜班的女警察有
人，而这90个人占整个女警察人数的18%，所以该警察局的女警察人数为：90÷18%=500人