The event in Earth’s history that most directly allowed life to exist on land is "Single-celled organisms released oxygen into the air when they photosynthesized." Thus, the correct option is C.
What are Single-celled organisms?
Single-celled organisms may be defined as those organisms that are constructed by only one cell. This single cell carries out all of the functions needed for the organism. They lack compartmentalization.
Single-celled organisms mainly bacteria evolve themselves in such a way that they released oxygen into the air when they photosynthesized. Such bacteria are known as photosynthetic bacteria.
These bacteria are only the source that brings this diversity among living entities on the earth's surface by making the availability of oxygen on this planet.
Therefore, the correct option for this question is C.
To learn more about Photosynthetic bacteria, refer to the link:
https://brainly.com/question/26152533
#SPJ5
