当蒸汽锅炉压力上升到到工作压力的（）时，应进行暖管，防止送汽时发生“水击”事故。
A.1/4
B.1/2
C.1/3
D.2/3
参考答案：D
大宗工业电价又称两部制电价，由基本电价及电度电价之和构成。 （）
Which of the following would be a likely theme for the next paragraph
A．Naturally changing ecological conditions.
B．Animals that have become extinct.
C．Achievements of the government Endangered Species Program.
D．Programs that have destroyed natural habitats.
