Fungi form lichens by living in a close relationship with an algae. The fungus provides a
protective home for the algae, and gathers mineral
nutrients from rainwater and from dissolving the
rock underneath. The algae gathers energy from
the sun using photosynthesis. Both organisms
share their nutrients with each other.
A. Commensalism
B. Parasitism
C. Mutualism
D. Competition

Commensalism

Explanation: Well you can already eliminate parasitism because that is when an organism leeches off another. Mutualism is when one organism needs to depend on another compared to A where both are benefited.  Then you can eliminate d because competition is when two organism compete with each other for survival not benefiting them both.

they deliver oxygen to the blood

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.