Geologically, What Is the Best Way to Explain the Thousands

Multiple Choice

Geologically, what is the best way to explain the thousands of metres of coral limestone beneath most atolls?

A) Sea level has fallen thousands of metres since the reef began to grow.
B) The volcano never reached the surface, but built a very thick cap of coral limestones from its deep submarine hot springs emissions.
C) The eroded volcano slowly sank as sea level remained steady or rose gradually.
D) An eroded volcanic seamount rose thousands of metres after the limestone formed.