For a message signal $m(t)=\cos \left(2 \pi f_{m} t\right)$ and carrier of frequency $f_{c}$ which of the following represents a single-side-band (SSB) signal?
- $\cos \left(2 \pi f_{m} t\right) \cos \left(2 \pi f_{c} t\right)$
- $\cos \left(2 \pi f_{c} t\right)$
- $\cos \left[2 \pi\left(f_{c}+f_{m}\right) t\right]$
- $\left[1+\cos \left(2 \pi f_{m} t\right] \cos \left(2 \pi f_{c} t\right)\right.$