Difficult# Group Automorphism: Structure of Automorphism Group of $Z/mZ$

ABSALG-KUCSFP

Let $\mathbb{Z}/m\mathbb{Z}$ be the additive group of integers mod $m$, for $m\ge 1$. The notation $\mathbb{Z}_m$ is also common for this group.

For a group $G$, let ${\rm Aut}(G)$ be the group of bijective group homomorphisms from $G$ to $G$ under composition $\circ$, namely,

for $\psi_1$, $\psi_2$ in ${\rm Aut}(G)$, the automorphism $(\psi_1\circ\psi_2)$ satisfies $(\psi_1\circ\psi_2)(g)=\psi_1(\psi_2(g))$, for all $g\in G$.

Which of the following are correct?

Select **ALL** that apply.