浮艇泵在维护保养时,每累计工作100h或使用6个月,更换一次发动机机油。
参考答案:对
She’ll spend as much time as she can to improve her spoken English.
A.speak English
B.to speak English
C.speaking English
D.speaks English
下列选项种,不会造成银镀层发暗、有斑点的是()。
A.银含量低
B.游离氰化物过少
C.有机杂质污染
D.银阳极不纯