ZD（J）9系列电动转辙机保养工作：检查零件是否受损的时间间隔为（）。
A.1个月
B.2个月
C.3个月
D.4个月
参考答案：A
预真空高压灭菌器，可达到的压力是
A．100kPa
B．105kPa
C．150kPa
D．160kPa
E．137kPa
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According to the lecture, what is "bartering"
A．Trying to get something for a cheaper price.
B．Exchanging one product or service for another.
C．Trading products in an unstable economy.
D．Specializing in the production of one goo
