大全226 再请教

226 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（A）

(E) to be a dwelling that must also operate as a business

我看了以前的讨论，但是不明白为什d不对?

in my opinion, in (D), there are two points which may be wrong:

1st, 'that'  is not so clear , meaning dwellings or being dwellings?

2nd, 'they' used here In (D) also figures on being dwellings instead of dwellings, so it is wrong to use ' they' but ' it '.

above all for reference only!