Answer:
c. Mutualism
Step-by-step explanation:
Mutualism -
Mutualism is a type of ecological interactions .
It refers to the connection between two or more species , by which all the species are dependent on each other and get benefit from each other , is referred to as mutualism .
For example -
vascular plants engaged in mutualistic interactions with mycorrhizae .
Similarly in the question ,
The microalgae living inside the corals , benefits each other .
Hence , from the given information of the question ,
The correct option form the given options is -
c. Mutualism .