Suppose signal $y(t)$ is obtained by the time-reversal of signal $x(t)$, i.e., $y(t)=x(-t),-\infty<t<\infty$. Which one of the following options is always true for the convolution of $x(t)$ and $y(t)$?
- It is an even signal.
- It is an odd signal.
- It is a causal signal.
- It is an anti-causal signal.