Product and Quotient Space Topologies – Lecture 13 (Topology)

In the product topology on X × Y, which collection serves as a basis?

1. A.All subsets of X × Y of the form A × B where A ⊆ X and B ⊆ Y
2. B.All complements of closed sets in X and closed sets in Y
3. C.All unions of open sets from X with open sets from Y
4. D.All sets of the form U × V where U is open in X and V is open in Y