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

b. Dinosaurs

The Mesozoic Era or what they commonly refer to as the age of the dinosaurs, is yet to be established as to what really did cause the extinction of life during this era. The popular belief and what is shared to the public to be remembered is that it was caused by an asteroid impact. The dust and ashes that it produced blocked the sky for days which caused the continuous death of organisms. In other sources, it can be said that massive volcanic eruptions occurred and filled the atmosphere with carbon dioxide. With the help of microbes eating carbon dioxide, they superheated the planet because in the process, these microbes eat carbon dioxide and release methane. Another one would be massive and continuous volcanic release of lava. It wasn't exactly determined if either one or maybe all of them occurred at once to wipe out life on that era.

4, two dominant and two recessive