Which of the following describes a difference between galaxies and solar systems? a. galaxies contain only moons, while solar systems contain planets. b. gravity holds solar systems in orbits but does not exist between stars in galaxies. c. a galaxy is a collection of millions of stars, while a solar system is a star and the planets around it. d. it's easier to use astronomical units to measure distances in the galaxy but use light years for measurements in a solar system.

The correct answer is Option C.

Explanation:

A galaxy is defined as the huge collection of gas, dust and billions of stars along with their solar system. All these systems are held together by the gravitational attraction. For Example: Milky Way.

A solar system is defined as the collection of a star, planets along with their moons, satellites of the planets, asteroids, meteoroids and comets. In the solar system planets revolve around the Star. For Example: Our Solar System has a star named Sun and eight planets revolve around it.

Hence, the correct answer is Option C.

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