The transfer function of a system is given by $H(s)=\frac{1}{s^{2}(s-2)}$. The impulse response of the system is
- $\left(t^{2 *} e^{-2 t}\right) \mathrm{U}(t)$ (* denotes convolution, and $\mathrm{U}(t)$ is unit step function)
- $\left(t^{*} e^{2 t}\right) \mathrm{U}(t)$
- $\left(t e^{-2} t\right) \mathrm{U}(t)$
- $\left(t e^{-2 t}\right) \mathrm{U}(t)$