过热蒸汽的温度与相应压力下饱和温度的差值称为（）。
A.过热度
B.临界温度
C.饱和温度
D.干度
参考答案：A
—What did Mary do last Sunday?
—She _____ her homework. [ ]
A. did
B. do
C. was doing
D. have done
“杀菌治脚气，请用达克宁”属于（）的广告。
A.商品
B.服务
C.观念
