Suppose that B is not ?s-connected. There exist ?-separated sets H
and G such that B = H ∪ G. This implies that H and G are nonempty and
G ∩ Cl∗
(H) = ∅ = H ∩ Cl(G). By Theorem 15, we have either A ⊂ H or
A ⊂ G. Suppose that A ⊂ H. Then Cl∗
(A) ⊂ Cl∗
(H) and G ∩ Cl∗
(A) = ∅.
This implies that G ⊂ B ⊂ Cl∗
(A) and G = Cl∗
(A) ∩ G = ∅. Thus, G is an
empty set. Since G is nonempty, this is a contradiction. Suppose that A ⊂ G.
By similar way, it follows that H is empty. This is a contradiction. Hence, B is
?s-connected.