Concept:A primary consumer is an organism that feeds directly on the producer.Explanation:In this food chain, cassava is the producer because it makes its own food through photosynthesis.The rat eats the cassava, so it feeds directly on the producer.Therefore, the rat is the primary consumer.The snake eats the rat, making it the secondary consumer.The hawk eats the snake, placing it as the tertiary consumer at the top of the chain.Answer:B. rat.