煤炭试验室一般都用破碎机械制备煤样,最常用的破碎机械有()、破碎缩分联合制样机、密封式粉碎机等。
A、颚式破碎机
B、双辊破碎机
C、锤式破碎机
D、单辊破碎机
参考答案:C
—They say there's a new restaurant nearby.
—Yes, and it ______ for no more than a week. [ ]
A. has been open
B. opens
C. is opening
D. is opened
()场所只能用水煤气管明设或暗敷。
A、干燥
B、潮湿或有腐蚀气体
C、导线与导线的交叉处
D、导线埋入墙内的