单项选择题

设线性无关的函数y1,y2,y3都是二阶非齐次线性方程y"+p(x)y'+q(x)y=f(x)的解,C1、C2是任意常数,则该非齐次方程是通解是()

A.C1-y1+C2y2+y3
B.C1y1+C2y2-(C1+C2)y3
C.C1y1+C2y2-(1-C1-C2)y2
D.C1y1+C2y2+(1-C1-C2)y3