“…It is a classical fact that X is ultranormal if and only if for every closed subset Y ⊂ X any f ∈ C * (Y, K) can be extended to some g ∈ C * (X, K), see [6,Theorem]. The following stronger result, for the proof see [15,Corollary 2.5.23] or [18,Theorem 5.24], partially motivates our work. Theorem 1.…”