Consider the system defined by $$\frac{d^{2}y}{dt^{2}}+(a+b)\frac{dy}{dt}+ab=x(t); a>0,b>0$$ can be realized using which impulse response function

A

$$h(t)=(e^{-at}+e^{-bt})u(t)$$

B

$$h(t)=(e^{-at} \times e^{-bt})u(t)$$

C

$$h(t)=(e^{at}+e^{-bt})u(t)$$

D

$$h(t)=e^{-(a+b)t} u(t)$$