In What Period Did All Modern Animal Groups First Appear

Question

In what period did all modern animal groups first appear in the oceans?
A) Cambrian
B) Silurian
C) Carboniferous
D) Permian

Accepted Answer

The Cambrian period is known as the "Cambrian explosion" because it is during this period that all modern animal groups first appeared in the oceans. This event was marked by a significant diversification and rapid evolution of life forms.