The example of an animal which has a complete digestive system is

Explanation

A complete digestive system is characterized by a digestive tract that has two separate openings: a mouth for ingestion and an anus for excretion. This allows for a more efficient and directional process of digestion and nutrient absorption. In this question, the roundworm is the correct example of an animal with a complete digestive system. Jellyfish have an incomplete digestive system with only one opening, which serves both as the mouth and the anus. Tapeworms lack a digestive system entirely because they absorb nutrients directly from the host's gut through their skin. Liver flukes, similar to jellyfish, also have an incomplete digestive system with a single opening. Therefore, the only correct choice is roundworm, which has a complete digestive system.