What is the passage mainly about?

Câu hỏi: Read the following passage and mark the letter A, B, C, or D to indicate the answer to each of the question.
Zoo officials say that they are concerned about animals. However, most zoos remain "collections" of interesting "items" rather than protective habitats. Zoos teach people that it is acceptable to keep animals in captivity. However, animals in zoos are bored, limited, lonely, and far from their natural homes.
Zoos claim to educate people, but in fact, visitors don't learn anything meaningful about the natural behavior, intelligence, or beauty of animals. Most zoo areas are quite small, and visitors can rarely observe animals' normal behavior in these unnatural spaces.
The animals are kept together in small spaces, with no privacy and little opportunity for mental stimulation or physical exercise. This results in abnormal and self-destructive behavior called zoochosis. A worldwide study of zoos found that zoochosis is common among animals in small spaces or cages. For example, Bears spend 30 percent of their time walking back and forth. These are all signs of distress.
Zoos also claim to save animals from extinction. However, zoos that breed endangered animals, such as big cats and Asian elephants, often do not release them to the wild. Ultimately, we will save endangered species only if we save their habitats. We also need to stop people from killing them. Instead of supporting zoos, we should support groups that work to protect animals and preserve their homes in the wild. (Adapted from www.usingenglish.com/forum/threads/zoo)
What is the passage mainly about?
A. The natural homes for zoos' animals.
B. The suffering zoos bring captured animals.
C. The things zoo officials concern.
D. The comfort for zoo visitors.