Which event occurred during the Mesozoic era?

a. Cyanobacteria begin to fill the air and water with oxygen.

b. Pangaea, the super continent, began to break apart.

c. The first plants lived on the land.

d. Humans lived on Earth.

Pangaea, the super continent, began to break apart during the Mesozoic era.

Explanation:

The distinct pieces of lands that today make seven different continents were once a single piece of land named Pangaea. Over a period of millions of years, this large lump of land gradually broke into several different pieces that slowly drifted apart from each other. Most of this breaking happened in the Mesozoic era that lasted for around 180 million-odd years. This period is said to have begun about 250 million years ago.