Dinosaurs, birds, early mammals and plants were major life-forms that existed in a. mesozoic era c. cenozoic era b. paleozoic era d. devonian era

A. Dinosaurs, birds, early mammals and plants were major life-forms that existed in the Mesozoic Era.

Explanation:

During the Mesozoic Era, the climatic conditions were arid, with the presence of a vast sandy desert, and with the compaction and consolidation a porous and permeable soil was formed, which allowed the creation of spaces for water storage, as is the case of aquifers on Earth.

In this period also occurred the appearance of dinosaurs, as well as their extinction. There were also small mammals in this Age, which were not the size of mammals commonly seen today, but they were ratlike in size. The first birds on the planet, as well as the first flowering plants, appeared in this Age. The Mesozoic Era is subdivided into three distinct Periods, which are marked by important events in Earth's evolutionary history, namely: Triassic, Jurassic and Cretaceous.

all three options are correct

i think it would be cleaveland browns