已知y1(X)与y2(x)是方程：y"+P(x)y'+Q(x)y=0的两个线性无关的特解，y1(x)和y2(x)分别是方程y"+P(x)y'+Q(x)y=R1(x)和y"+p(x)+Q(x)y=R2(x)的特解。那么方程y"+p(x)y'+Q(x)y=R1(x)+R2(x)的通解应是：
A.c1y1+c2y2
B.c1Y1(x) +c2Y2 (x)
C.c1y1+c2y2 +Y1(x)
D.c1y1+c2y2 +Y1 (x) +Y2 (x)
正确答案是D