The differential equation which has $y=C_1{e}^x+C_2{e}^{-2x}$ as its general solution is:

$($a$)y^{\text{'}\text{'}}-y^{\text{'}}-2y=0$

$($b$)y^{\text{'}\text{'}}+y^{\text{'}}-2y=0$

$($c$)y^{\text{'}\text{'}}+y^{\text{'}}+2y=0$

$($d$)y^{\text{'}\text{'}}+2y^{\text{'}}+y=0$

$($e$)$ None of the above.