The correct answer is (b), primary consumers.
Producers are organisms that can make their own food using sunlight, water, and carbon dioxide. Primary consumers are organisms that eat producers. Secondary consumers are organisms that eat primary consumers. Tertiary consumers are organisms that eat secondary consumers.
Termites are insects that eat wood. Wood is made up of cellulose, which is a type of plant material. Cellulose is not digestible by most animals, but termites have a special type of bacteria in their gut that can digest cellulose. This allows termites to eat wood and get the nutrients they need.
Therefore, termites are primary consumers because they eat producers (wood).