Correct option :(C).
According to ques,
\[y~=~{{e}^{x}}~\left( A\text{ }cos~x~+\text{ }B\text{ }sin~x \right)\]
Differentiating both sides with respect to x,
If y = e–x (A cos x + B sin x), then y is a solution of: (A) d^2y/dx^2+2dy/dx=0 (B)d^2y/dx^2-2dy/dx+2y=0 (C)d^2y/dx^2+2dy/dx=2y=0 (D)d^y/dx^2+2y=0
If y = e–x (A cos x + B sin x), then y is a solution of: (A) d^2y/dx^2+2dy/dx=0 (B)d^2y/dx^2-2dy/dx+2y=0 (C)d^2y/dx^2+2dy/dx=2y=0 (D)d^y/dx^2+2y=0