Which event occurred during the Mesozoic era? Cyanobacteria filled the water and air with oxygen.

Early humans began to make tools, harvest plants, and make cave paintings.

Pangaea began to break apart into many continents separated by shallow seas.

Pangaea, the super continent, was formed.

Pangea began to break apart.

Explanation:

Humans wouldn't exist for millions more years. Pangea existed before the Mezoic, and the Cyanobacteria doesn't make sense.  (Not an expert though.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.