现况调查主要分析指标是：（）
A.发病率
B.病死率
C.死亡率
D.患病率
E.罹患率
参考答案：D
At that time, he was studying in_______ university. And it was a famous one.
A．/
B．the
C．a ,
D．an
养殖水体最适的PH值范围（）.
A、6.5-7.5
B、7.5-8.0
C、8.0-8.5
