Purple Martins Are the Largest Species of Swallow in North

Purple martins are the largest species of swallow in North America.In the Eastern United States,they breed almost exclusively in large colonies in artificial martin houses and hollowed- out gourds hung by martin enthusiasts.Given this information,which of the following would be a valid inference?

A) In the eastern United States,purple martins are generalists with a broad ecological niche.
B) Purple martins and martin enthusiasts exhibit a relationship that can best be described as commensalism.
C) In the eastern United States,purple martins are specialists because they rely almost solely on humans for nesting sites.
D) In the eastern United States,purple martins have a size advantage over other swallows and are able to outcompete them for nest sites.