Polar bears in captivity exhibit obsessive patterns of behavior such as pacing back and forth on the same spot, swinging their heads from side-to-side, and using their paws to repeatedly stroke their head. Such behaviors are signs of stress. They behave this way even when zoos design their living areas to include elements of the polar bear's natural environment. This shows that polar bears do not do well in captivity.

Which of the following statements best expresses the main conclusion of the above argument?

a. Conditions of captivity are poor substitutes for the polar bear's natural habitat.

b. Polar bears are not well suited for captivity.

c. Stressed polar bears exhibit obsessive patterns of behavior.