The correct option is A 1st Era - Paleozoic, 2nd Era - Mesozoic, 3rd Era - Cenozoic
In geological peroids of earth, four Eons are there - Azoic/Hadean, Archaeozoic, Proterozoic, Phanerozoic. In phanerozoic Eon (Eon 4), three Eras are there. They are: 1st Era - Paleozoic, 2nd Era - Mesozoic, 3rd Era - Cenozoic