伤寒患者常见的热型为（）。
A．稽留热
B．歇热
C．不规则热
D．弛张热
E．体温过低．
参考答案：A
When I try to find ______that prevent so many people from taking part in the program, it seems to me that there are two main causes.
A．why it does
B．what it does
C．what it is
D．why it is
下列不属于描述性研究的是（）
A.历史常规资料的分析
B.现况研究
C.生态学研究
D.随访研究
E.临床诊断试验
