A species of fish has experienced an increase in its carrying capacity. What could explain this increase in carrying capacity?

a. The species has experienced an increase their food.
b. One of its competitors for food has experienced an increased population.
c. The species lives mutually with another species that has recently experienced a
decline in its population due to parasites.
d. The species lives in an estuary that has recently experienced a large influx of
freshwater due to flooding of the nearby rivers and causing plant loss.