三位气缸是用两个缸径相同、行程不同的同类气缸（）组合构成。
参考答案：串接
They were abroad during the months when we were carrying out the investigation, or they _____ to our help.
A．would have come
B．could come
C．have come
D．had come
法西斯专政首先出现于第一次世界大战后的______
A．德国 B．意大利C．日本 D．西班牙
