下列哪一项常用作计算某病发病率的分母（）
A.观察到的新病例数
B.观察到的病例数
C.健康人数
D.观察人年数
E.无症状的病例数
参考答案：D
There are ______ people in the supermarket. It's so crowded. [ ]
A．hundred
B．hundreds
C．hundred of
D．hundreds of
Vicky likes the book __________she borrowed from Jim.
A．who
B．that
C．whom
D．whose
