Most spiral galaxies have rotation curves that
A) decrease rapidly with increasing radius in the disk, indicating no dark matter is present.
B) increase drastically with increasing radius.
C) decrease rapidly with increasing radius in the disk, indicating the presence of dark matter.
D) stay constant out to large radii in the disk, indicating that no dark matter is present.
E) stay constant out to large radii in the disk, indicating the presence of dark matter.
Ans: E) stay constant out to large radii in the disk, indicating the presence of dark matter.
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