By Observing Gas Clouds Orbiting the Centers of Galaxies, We

Multiple Choice

By observing gas clouds orbiting the centers of galaxies, we have learned that galaxies are made mostly of dark matter. In these observations

A) the high speeds of the gas clouds show that they are being pushed by some unseen material.
B) the high speeds of the gas clouds show that they are gravitationally attracted to the center by unseen material.
C) the low speeds of the gas clouds show that they are gravitationally attracted to the center by unseen material.
D) the light from the gas clouds is obscured by some unseen material.
E) the low speeds of the gas clouds show that they are being slowed by some unseen material.