For which additive submonoids $M$ of nonnegative rationals is $F[X;M]$ AP?
We characterize the submonoids $M$ of the additive monoid $\Q_+$ of nonnegative rational numbers for which the irreducible and the prime elements in the monoid domain $F[X;M]$ coincide. We present a diagram of implications between some types of submonoids of $\Q_+$, with a precise position of the monoids $M$ with this property.