什么是顶棚过热器？
参考答案：
顶棚过热器布臵在炉膛和水平烟道顶部，主要吸收炉膛火焰辐射热、烟气流中的一小部分辐射热及少量对流热，属于辐射式过热器。
To our relief, at last the opening ceremony of the sports meeting we had been looking forward to _____
on time.[ ]
A. had started
B. starting
C. started
D. being started
各级人民政府在公路建设和管理中的职责有哪些？
