乙烯制冷压缩机返回线有（）。
A．四返一
B．四返二
C．四返三
D．四返四
参考答案：A, B, C
— Jack, I lost your ball at school. I suppose I should pay for it.
— Oh. ______. It was just an old ball anyway. [ ]
A. Take it easy
B. By no means
C. You got it
D. Forget it
在可摘局部义齿制作中，下面哪项是塑料填塞最宜的时期
A．湿砂期B．粥状期C．丝状期D．面团期E．橡皮期
