在锅炉额定工况下，省煤器中产生的（）占（）的百分数称为省煤器的沸腾率。
参考答案：蒸汽量；额定蒸发量
I saw a cat ____________ yellow socks. [ ]
A. on
B. or
C. in
The teacher often tells us to keep windows ________ after class. [ ]
A. open
B. opened
C. opening
D. to open
