Answer:
Mammals first appeared
Explanation:
The dinosaurs became extinct one million years after the Cenozoic era started. The mammals first appeared as the modern culture first appeared in that era.
Answer:
a layer or a series of layers of rock in the ground. ,
a level or class to which people are assigned according to their social status, education, or income.
Explanation:
A duplication is a mutation where the chromosome carries repetitive sets for a gene.
