This picture represents humoral immunity, please read through it, and if you dont understand which option is your answer then i would recommend you read more about this topic, if you want it to be done fast, you can read this http://www.s-cool.co.uk/a-level/biology/immunity/revise-it/the-third-line-of-defence
I hope you can come up with the answer on your own as it will be a good thing for you in your future exams :)
Surely i can help you if you dont understand something so just ask :D
Answer: Operant Conditioning
Some bears must have had undergone operant conditioning that is why they open their mouths for teeth cleaning and present their paws for nail clipping.
Operant conditioning is a form of learning in which a reward or punishment is given for some voluntary behavior.
Bears that have undergone operant conditioning are called food-conditioned bears. They are dangerous but learned to approach humans, or frequent human-occupied sites, in search of food (reward).
Dunkleosteus is an extinct genus of arthrodire placoderm fish that existed during the Late Dev Devonian period, about 360-380 million years ago.