在病例对照研究中，变量的测量应尽可能的采用（）。
A.计数变量
B.有序分类变量
C.无序分类变量
D.定量或半定量
E.定性
参考答案：D
It was only with the help of the local guide________________.
A．was the mountain climber rescued
B．that the mountain climber was rescued
C．when the mountain climber was rescued
D．then the mountain climber was rescued
应答器相邻布置时，应答器的最小间隔为12米
