Question

which of the following eras in earths history is the longest?
pre - cambrian
paleozoic
mesozoic
cambrian
cenozoic

Explanation:

The Precambrian era spans about 4 billion years, from the formation of the Earth to the start of the Cambrian period, much longer than the other eras listed. The Paleozoic, Mesozoic, and Cenozoic eras are much shorter in comparison. The Cambrian is a period within the Paleozoic era.

Answer:

Precambrian