若3a2-a-2=0，则5+2a-6a2=（ ）。
1
The police still have found the lost child, but they're doing all what they _____. [ ]
A. can
B. may
C. must
D. should
CRH1A型动车组受电弓升弓所需最小压力为（）kPa。
A.250
B.300
C.320
D.350
