The passage suggests that if the scientists mentioned in the highlighted text are correct in their speculations, the large multi-ring impact basins on the moon with the most significant negative gravity anomalies probably
a) were not formed early in the moon's history
b) were not formed by the massive ejection of crustal debris
c) are closely surrounded by other impact basins with anomalously low gravity
d) were created by the impact of multiple large impactors
e) were formed when the moon was relatively elastic