Each of them ______ a dictionary. [ ]
A. have
B. has
C. is
D. are
B
环烯醚萜属于
A．单萜B．倍半萜C．二萜D．三萜E．甾体
某容器内的压力为1MPa。为了测量它，应选用量程为（）MPa的工业压力表。
A.0~1
B.0~1.6
C.0~2.5
D.0~4.0
