For $n\ge 1$, the dihedral group $D_n$ is the group generated by two elements $r$, $s$, where:

the element $r$ has order $n$, the element $s$ has order $2$, and the element $sr$ has order $2$.

Its presentation in terms of generators and relations is therefore:

$D_n=\langle r,s\mid r^n=s^2=(sr)^2=1\rangle$, where $1$ is the neutral element.

Which of the following are true?