等比数列{an}中,a3^2=a1*a5
a4^2=a3*a5
a2^2=a1*a3
又 an>0,a1=81,a5=16,
所以 a3^2=81*16,a3=9*4=36
a4^2=36*16,a4=6*4=24
a2^2=81*36,a2=9*6=54
所以 前四项的和是：a1+a2+a3+a4
=81+54+36+24
=195.选B.
等比数列{an}中,a3^2=a1*a5
a4^2=a3*a5
a2^2=a1*a3
又 an>0,a1=81,a5=16,
所以 a3^2=81*16,a3=9*4=36
a4^2=36*16,a4=6*4=24
a2^2=81*36,a2=9*6=54
所以 前四项的和是：a1+a2+a3+a4
=81+54+36+24
=195.选B.