Operating a rotary pump at speeds in excess of design requirements could cause（）.
A. decreased clearances between rotating parts
B. decreased slippage to the suction side of the pump
C. air binding in the discharge ports
D. erosion and excessive wear
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电视节目从一个国家引入另一个国家时，如果这个节目的文化折扣较小，则被引入国家的观众就很难喜欢。
A. 正确
B. 错误
钢球式磨煤机的钢球充满系数为（）。
A. 0.4~0.5
B. 0.2~0.3
C. 0.1~0.2
D. 0.5~0.6
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