深冷装置的透平膨胀机启机前应先进行节流制冷，使温度达到（）K左右时，启动透平膨胀机。
A.263
B.273
C.283
D.293
参考答案：B
(2014·东北三校模拟)We had just covered half the journey________the engine failed and we could do nothing but wait for help.
A．before
B．since
C．when
D．until
以下哪项不是升浮药物的作用( )
A．透疹
B．涌吐
C．安神
D．开窍
E．发表散寒
