We couldn't go out _____ it is too cold today. [ ]
A. but
B. if
C. or
D. because
答案:D
在如图所示的实验中,李明发现:硬纸片在木梳上划得快时音调高,划得慢时音调低.这表明:______.
竹叶石膏汤原方中麦冬与半夏的配伍比例是()
A.2:1
B.3:1
C.5:1
D.6:1
E.7:1