单选题 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?

【正确答案】 D
【答案解析】[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