Which of the following appeared during the mesozoic era?
a. birds
c. mammals
b. dinosaurs
d. all of the above

Answer;

-All the above

-Birds, mammals and Dinosaurs, all appeared during the Mesozoic Era.

Explanation;

-The Mesozoic Era was an Era that lasted for about 180 million years, and is divided into three periods, the Triassic, the Jurassic, and the Cretaceous.

-During this time, many modern forms of plants, invertebrates, and fishes evolved. On land, dinosaurs were the dominant animals, while the oceans were populated by large marine reptiles, and Pterosaurs ruled the air.

-It is said that birds are a group of theropod dinosaurs that originated during the Mesozoic Era. The first mammals evolved from a population of vertebrates called therapsids, at the end of the Triassic period and coexisted with dinosaurs throughout the Mesozoic Era.

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.