First mammal occur in which era -period ?

Options

A. Permian-Palaeozoic
B. Triassic-Mesozoic
C. Tertiary-Coenozoic
D. None of these

Answer

B

Explanation

In Triassic period of Mesozoic era, the primitive amphibians became extinct, some of the reptilian group returned to sea-life and some invaded air. Another important event which took place late in Triassic period was the first appearance of mammals, which retained egg laying habit.