若{an}是公差为1的等差数列，则{a2n-1+2a2n}是（　　）A．公差为3的等差数列B．公差为4的等差数列C．公差

设{an}的公差为d，则d=1，设cn=a2n-1+2a2n，则cn+1=a2n+1+2a2n+2，∴cn+1-cn=a2n+1+2a2n+2-a2n-1-2a2n=6d=6，故选C．