Correct answer
which situation involves mainly biotic factors?

a drop in the ph of ocean water prevents coral from growing properly, which harms the coral reef ecosystem.

a fungus wipes out a bat population, which allows the mosquito population to increase and spread disease to people.

dust from a volcanic eruption blocks sunlight to earth's surface, and as a result the weather gets colder.

a drought causes crops to die, and as a result cattle go hungry.