装置循环氢中断后，如果反应器床层超温，可采取的措施是（）。
A、启动紧急泄压阀
B、打冷氢
C、床层通氮气
D、降低进料量
参考答案：A
The number of people invited to the party ____ fifty, but a number of them ____ absent for different reasons.
A．were; was
B．was; was
C．was; were
D．were; were
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