A:Having told him
B:Having been told him
C:Though he had been told
D:He was told
如图是某通道的侧面示意图,已知AB∥CD∥EF,AM∥BC∥DE,AB=CD=EF,∠AMF=90°,∠BAM=30°,AB=6m.
在各项均为正数的等比数列{an}中,a1=2,且2a1,a3,3a2成等差数列.