Answer
A
Work Step by Step
Option B is incorrect. A carnivore is actually a consumer, probably on the secondary or tertiary level. Carnivores eat other animals.
Option C is incorrect. An omnivore eats both plants and animals, so it is a consumer.
Option D is incorrect. A detritivore eats detritus, which is what remains after a decomposer breaks down dead organisms. Detritivores are also consumers.
Option A is correct. Algae is a primary producer.