Suppose That an Astronaut Trained in Geology Lands on the Surface

Suppose that an astronaut trained in geology lands on the surface of a distant planet and finds that most of the rock at the landing site is composed of limestone. The astronaut can immediately surmise that the location of the landing site:

A) was once subjected to enormous pressure and high temperature deep under the planet's surface, causing the original rock to change structure.
B) solidified from molten rock close to the surface of the planet.
C) solidified from molten rock deep beneath the surface of the planet.
D) was once the bed of an ancient ocean.