Which of the following best describes how the Great Barrier Reef was formed?
a. When sea levels decreased significantly during the ice age, patches of rock and coral emerged
b. When sea levels rose at the end of the ice age, the coastal region was submerged and corals grew on the rocky fringes of the continental shelf
c. The coastline and barrier reef were already established prior to the ice age, but the major rise in seawater temperature following this period provided an optimal habitat for corals to grow significantly more