Let $G$ be an infinite group that is not simple. If $B$ is a subgroup of $G$, must $B$ necessarily be not simple as well?
I know that if $N$ is some proper normal subgroup of $G$, then $B\cap N$ is a normal subgroup of $B$. But we may also have that $B$ intersects trivially with $N$.
If no, is there a counter example? Would be grateful if anyone can enlighten me.