下列八种机械零件:
a.汽车发动机的阀门弹簧;b.起重机的抓斗;c.气轮机的叶轮;d.车床变速箱中的齿轮;
e.纺织机的织梭;f.飞机的螺旋桨;g.柴油机的曲轴;h.自行车的链条。
其中有_______专用零件而不是通用零件。
Goods are carried by several of transport--on road or rail, by sea or air.
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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