Embeddings into (a)-spaces and acc spaces

A space X is said to be an (a)-space provided that for every open cover U of X and every dense subspace D of X there exists a closed in X and discrete subspace F ⊂ D such that St(F, U) = X. We show that every Tychonoff space can be represented as a closed subspace of a Tychonoff (a)-space. Also we consider closed Gδ-subspaces.