Find the General Solution of the Linear Differential Equation $y^{\prime}+3 y=e^{-3 x}$

Find the general solution of the linear differential equation $y^{\prime}+3 y=e^{-3 x}$ .

A) $y=(x+C) e^{-3 x}$
B) $y=(x+C) e^{3 x}$
C) $y=1+C e^{3 x}$
D) $y=C e^{-3 x}$