The amplitude modulated wave form $s(t)=A_{c}\left[1+K_{a} m(t)\right] \cos \omega_{c} t$ is fed to an ideal envelope detector. The maximum magnitude of $\mathrm{K}_{0} m(t)$ is greater than $1$. Which of the following could be the detector output?
- $\mathrm{A}_{c} m(t)$
- $\mathrm{A}_{c}^{2}\left[1+\mathrm{K}_{a} m(t)\right]^{2}$
- $\left|\mathrm{A}_{c}\left[1+\mathrm{K}_{a} m(t)\right]\right|$
- $\mathrm{A}_{c}\left[1+\mathrm{K}_{a} m(t)\right]^{2}$