In our Solar System the mass is primarily at the center, so the orbital speed of the planets decreases with distance. In a galaxy the orbital speed remains the same at large distances. What does this tell us about the distribution of mass in a galaxy?

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Explanation:

In order to be able to answer this question effectively and efficiently we have to consider the Newton's law of Universal gravitation which is given by the mathematical representation below;

Gravitational force, F = G (m1 × m2) / r^2.

Where G = Gravitational constant, m1 and m2 and the masses of body one and two respectively and r = distance.

So, we can deduce that the mass(in form of kinetic energy) increase at large distance and this makes the speed to reduce.

all three options are correct