锅炉运行时，从水垢的内表面到炉水，热量以（）方式传递给炉水。
A、对流
B、导热
C、辐射
D、导热、对流
参考答案：A
He is doing ______ experiment. [ ]
A. /
B. a
C. an
Did she read books? [ ]
A. No, she didn't.
B. No, he didn't.
C. Yes, I did.
