Sponges and Cnidarians Are Among the Fossilized Animals Found in Both

Sponges and cnidarians are among the fossilized animals found in both the Ediacara Hills and the Burgess Shale from the Rocky Mountains of British Colombia. This observation requires that

A) ancestral sponges and cnidarians had formerly been terrestrial animals.
B) North America and Australia were united to each other about 550 million years ago (mya) .
C) land that now comprises the Ediacara Hills and the Rocky Mountains was underwater about 550 million years ago.
D) only sponges and cnidarians existed at the time the sediments were deposited.