Difference between second level consumer and third level consumer

Second-level Consumers - consumers that get their energy from first-level consumers and/or producers. Carnivores - organisms that eat only other animals. Third-level Consumers - consumers that eat second-level consumers and/or first-level consumers.

The answer is commensalism.

Commensalism is a relationship between two organisms in which only one of them has benefit, and the other one is not affected. In this example, the Great Burdock's plants spread their seeds using animals, so they benefit from this relationship. On the other hand, animals neither have benefits not are harmed from the relationship.
Therefore, the relationship between the Great Burdock plants and animals is the example of commensalism.