The largest unit of geologic time in the list below is:

From largest to smallest, this hierarchy includes eons, eras, periods, epochs, and ages. All of these are displayed in the portion of the geologic time scale shown below. The Phanerozoic Eon represents the time during which the majority of macroscopic organisms — algae, fungi, plants and animals — lived.

Explanation:

Hope this helps you :)

i think it's letter a.