Let $R$ be a ring with identity. Let $M$ be a left unital $R$-module and $N$ a right unital $R$-module.
Denote by $M^\ast$ the left $R$-module homomorphisms from $M$ to $R$ and by $N^\ast$ the right $R$-module homomorphisms from $N$ to $R$. These are called the dual modules to $M$ and $N$, respectively.
Which of the following are always correct?
Select ALL that apply.