补充126，答案A中dwelling和后面的 businesses单复数怎么不一致呀？

补充126，答案A中dwelling和后面的 businesses单复数怎么不一致呀？

Cooperative apartment houses have the peculiar distinction of being dwellings that must also operate as businesses.
(A) of being dwellings that must also operate as businesses
(B) of dwellings that must also operate like business
(C) that they are dwellings that must operate like business
(D) that, as dwellings, they must also operate like businesses
(E) to be a dwelling that must also operate as a business

是一致的呀~