Two hypothetical discoveries in Part A deal with moons that, like Earth's moon, are relatively large compared to their planets. Which of the following best explains why finding 1 planet with such a moon is consistent with the nebular theory, while finding 6 planets with such moons is not consistent?
a. Unusually large moons form in giant impacts, which are relatively rare events.
b. The nebular theory says that only planets at least as large as Earth can have large Moons, and 6 Earth-size planets would not be likely to form in one solar system.
c. The nebular theory holds that moons of any size should be rare, so finding 1 is not too surprising but finding 6 would be very surprising.
Answer : a. Unusually large moons form in giant impacts, which are relatively rare events.
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