化学分析
参考答案：
是指以化学反应为基础的分析方法。
Mary decided not to work on the program at home because she didn’t want her parents to know what she __________.
A．has done
B．had done
C．was doing
D．is doing
产后出血的定义是指胎儿娩出后24小时内出血量超过（）
A.300ml
B.350ml
C.400ml
D.450ml
E.500ml
