The answer is b. rabbits.
Rabbits are herbivores and thus primary consumers in a trophic pyramid.
On the first trophic level are producers. Trees, together with other plants, are able to make their own food, so they are producers. Herbivores, such as rabbits, eat plants. So they are primary consumers and just above the producers in the trophic level. Secondary consumers, which are carnivores, eat herbivores. An example is a snake. Tertiary consumers are carnivores too. They eat other carnivores. For example, a hawk is a tertiary consumer.