2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/73605We prove that every countable subgroup of a compact metrizable abelian group has a characterizing set. As an application, we answer several questions on maximally almost periodic (MAP) groups and give a characterization of the class of (necessarily MAP) abelian topological groups whose Bohr topology has countable pseudocharacter.12 pagesGeneral Topology54H11text