[单选题] 在各项都为正数的等比数列{an}中，首项a1=3，前3项和为21，则a3+a4+a5=( )-湖北继续教育网网校

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[单选题][单选题] 在各项都为正数的等比数列{an}中，首项a1=3，前3项和为21，则a3+a4+a5=( )

A33

B72

C84

D189

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