an=a1+(n-1)da3=a1+2da9=a1+8d因为a1,a3,a9成等比数列,所以a3/a1=a9/a3所以(a1+2d)^2=a1(a1+8d)化简得a1=dan=a1+(n-1)d=na1所以(a1+a3+a9)/(a2+a4+a10)=(a1+3a1+9a1)/(2a1+4a1+10a1)=13/16选A