在平行投影中，两人的高度和他们的影子（ ）．
对应成比例
—Is Mr Black in ?
—No, he is out. ________?
—No, thank you. [ ]
A. What's up
B. Can I take a message for you
C. Can I hold on a moment
D. When will you call him back.
泡敌属于（）消沫剂。
A.天然油脂
B.聚醚类
C.硅酮类
D.脂类
