the time when life began at what era Cenozoic Era c. Mesozoic Era b. Paleozoic Era d. Cretaceous Period

The life began during the time of Paleozoic Era.

Explanation:

The Phanerozoic Eon is classified as three era namely:

The Paleozoic era or era of ancient life The Mesozoic era or era of middle life The Cenozoic era or era of new life

The initiation of life was seen during Paleozoic era. It began 542 million years back with the development of complex living things and finished 251 million years prior with the biggest mass elimination the world has ever experienced. It is the most seasoned and longest period of Phanerozoic Eon.

cretaceous period

Explanation:

the abiogenesis started in - 4100 millions years ago.

source: curtis. biology 8th edition.