The correct answer is A. It eats plants and converts the sugar in plants into ATP by cellular respiration.
Explanation:
Herbivores are animals that can not make their own food and depends on others to get food so they are heterotrophs. Herbivores are specialized to eat plants and gain energy from it.
The process they use to release energy from the ingested plant material is called cellular respiration. In this process, they absorb the carbohydrate(sugar) reserve present in the plant material and oxidize it to produce ATP in the cell. This ATP provides energy to the plant to perform metabolic activities. So the correct answer is A.