Which of the following is the best description of a nebula?

a
a large cloud of dust and gas
b
a dense cluster of billions of stars
c
a single sun surrounded by planets and asteroids
d
a large cloud of comets and asteroids surrounding a solar system

a large cloud of dust and gas

The best description of a nebula is option a: a large cloud of dust and gas.

The best description of a nebula is option a: a large cloud of dust and gas.

To arrive at this answer, it is important to understand the definitions of the given options and then determine which one accurately represents a nebula.

Option b describes a dense cluster of billions of stars, which is known as a galaxy or a star cluster, not a nebula.

Option c refers to a single sun surrounded by planets and asteroids, which is a description of a star system like our own, not a nebula.

Option d describes a large cloud of comets and asteroids surrounding a solar system, which is more akin to the Oort cloud, a theoretical region of icy bodies located on the outskirts of our solar system, rather than a nebula.

Therefore, option a, describing a large cloud of dust and gas, is the most accurate description of a nebula.