Final answer:
Given that both gibbons and orangutans are arboreal primates, gibbons would be the most appropriate choice to live in a building similar to the main primate house designed for arboreal species.
Step-by-step explanation:
The question asks which animals will live in a building that is similar to the main primate house in the context of a new housing structure designed for a zoo's primate section. Given the provided information regarding the habitat and behavior of great apes, we can determine the best match for a building similar to that of the existing main primate house.
Gibbons, as described, are lesser apes that are highly arboreal, swing through trees with their long arms, and display low sexual dimorphism. They require expansive vertical space to accommodate their brachiating (tree-swinging) lifestyle, which would be fitting for a building similar to that of the arboreal orangutans. The great apes such as chimpanzees, gorillas, and orangutans share a similar skeletal structure, indicating similar needs in housing design to some extent.
However, due to the specific needs of each species, such as the gorilla's need for ground space due to their terrestrial lifestyle compared to the highly arboreal lifestyle of the orangutans and gibbons, it would be suitable to house gibbons in a building similar to that of the main primate house which accommodates arboreal species. Therefore, the answer is gibbons (C).