1. 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

已经看过前人的讨论，但是我对这句话的意思还是不明白，另外对于dwellings that must also operate as businesses 也不明白是什么意思 请指教 谢谢