Question

in which era did mammals emerge?
cenozoic
mesozoic
paleozoic
precambrian

Explanation:

Mammals emerged during the Mesozoic era. The Cenozoic era is known for the diversification of mammals after the extinction of non - avian dinosaurs. The Paleozoic era was dominated by other groups like amphibians and early reptiles. The Precambrian is too early, long before complex vertebrates like mammals. So, based on geological time scale knowledge, the Mesozoic is when mammals first appeared.

Answer:

Mesozoic