煤粉着火特征的常规性指标包括（）。
A、挥发分
B、最低着火温度
C、灰分和水分
D、发热量
参考答案：A, C, D
He _____ from among them and _____.[ ]
A. choose, took it off
B. chose, take away it
C. choosed, took it off
D. chose, took it away
产生脲酶的是（）.
A.空肠弯曲菌
B.幽门螺杆菌
C.以上两者均是
D.以上两者均否
E.其他
