What Is the Relationship Between a Giant Molecular Cloud and an H

What is the relationship between a giant molecular cloud and an H II region?

A) They are two names for the same entity.
B) In giant molecular clouds, H II regions surround ultraviolet-emitting stars (types O and B) , which have ionized the hydrogen around them.
C) In H II regions, giant molecular clouds are concentrations of other molecules like CO and H₂O.
D) Giant molecular clouds evolve into H II regions as the molecules other than hydrogen are used up in star formation.