The cenozoic was a time of
a. mountain building
c. global warming
b. continental breakup
d. slow, global extinctions

The right answer is A. mountain building.

The Cenozoic is divided into three systems (the first two form what is informally called the Tertiary Era):

1 ° the Paleogene system or Eogene, (is divided into Paleocene, Eocene, and Oligocene).

2 ° the Neogene system,

3 ° the Quaternary system .

At the Eocene, the tectonic phase that affects the Pyrenees and Provence cause, as early as the Upper Eocene, folds even in the Iberian chains. At the Lutetian, India hits and stamps Eurasia, causing the formation of the largest mountain range, the Himalayas, whose major phase of uplift will occur later, during the Neogene.