Question

the stars and all the other matter in a galaxy are held together by which of the following? dark matter inertia magnetism gravity

Explanation:

Gravity is the force that attracts objects with mass towards each other. In a galaxy, the gravitational pull of the combined mass (including stars, gas, dust, and dark matter) keeps all the components together. Dark matter contributes to the mass but doesn't directly "hold" in the sense of a force like gravity. Inertia is the tendency of an object to resist changes in its state of motion and isn't a force that binds matter. Magnetism is a force related to magnetic fields and isn't the dominant force holding a galaxy together.

Answer:

gravity