Apopulation of jellyfish has shown a sharp decline. what types of factors should be investigated? (the last answer was wrong)

What types of factors should be investigated?

D. Both abiotic and biotic factors in their ecosystem

Abiotic factors are non-living parts of an environment, while Biotic factors are the living parts of an environment. That being said, you should investigate both when the population of jellyfish show a sharp decline, in order to find out the cause in the decline of jellyfish.

thinking it would be d not too sure but i think it's right