The solution of differential equation $y''+3y'+2y=0$ is of the form

$C_1e^x+C_2e^{2x}$

$C_1e^{-x}+C_2e^{3x}$

$C_1e^{-x}+C_2e^{-2x}$

$C_1e^{-2x}+C_2e^{-x}$