Which of the following best explains why the Moon's orbital period and rotation period are the same?
A) The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period.
B) The Moon was once closer to Earth, but the force of gravity got weaker as the Moon moved farther away.
C) The law of conservation of angular momentum ensured that the Moon must have the same amount of rotational angular momentum as it has of orbital angular momentum.
D) The equality of the Moon's orbital and rotation periods is an extraordinary astronomical coincidence.
The answer is A) The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period.
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