Question

what is a nebula?
the core of a massive star
a cloud of gas and dust in space
a swirling disk with a lot of gravity
the debris remaining after a supernova

Explanation:

A nebula is an interstellar cloud made up of gas (mostly hydrogen and helium) and dust in space. It can be a site of star - formation. The other options describe different astronomical objects or parts of star - related processes.

Answer:

a cloud of gas and dust in space