A black hole in the universe is - a) An empty region in space b) A moon that is always turned to its dark side c) A massive collapsed star

The extremely small objects in space that at one time were enormous stars are called black holes.

Option c) A massive collapsed star

Explanation:

A black hole forms as a result of the collapse of the center of a massive star into itself. This process is known as supernova.

The gravitational pull of the black hole is enormously strong enough that nothing can escape it not even any electromagnetic radiations or light and absorbs everything that tries to cross it as a result of enormously massive star into a very tiny or small space.