The following diagrams are supposed to represent hypothetical galaxies seen edge-on. The left diagram is a diagram without dark matter, while the right diagram shows a galaxy with a dark matter halo. Consider the force of gravity on the stars shown in the figures ( which you can assume all have the same mass):

    A ) The force of gravity on star C is greater than the force of gravity on star D because it is closer to the center of the galaxy
    B) The force of gravity on star D is greater than the force of gravity on star C because more dark matter is pulling on it.
    C) It's hard to tell because both statements (A) and (B) are true
    D) Star D has to be travelling slower than star C because it is farther away.

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