What occurred while the surface rocks of the Moon were impacted, creating a fine dust? A. Lava flows formed maria. B. Earth and a planetesimal collided. C. The Moon became geologically inactive. D. Bombardment by meteoroids formed the highlands.

Earth and a planetesimal collision occurred while the surface rocks of the Moon were impacted, and was creating a fine dust. This is also called the giant impact, in which the Moon was a debris from the collision of the Earth and the Mars-sized body four billion years ago.