锅炉点火前应了解锅炉的安装（）、烘炉、煮炉、水压试验、安装和修理质量验收情况。
A.大修，检验
B.小修
C.抢修
D.试运
参考答案：A
The traffic is moving very slowly as so many cars on their way back to Shanghai.
A．am
B．is
C．are
D．be
洁净室与非洁净室、不同洁净级别的相邻房间压差应为多少？
