All animals can trace their lineage to a common ancestor that lived in the see concept 32.2 (page 673)

The best answer is Neoproterozoic era. Neoproterozoic Era is the unit geologic time from 1000 to 541 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran Periods. It is preceded by the Mesoproterozoic  era and succeeded by the Paleozoic era.

Ibelieve its b but u might have to