21.While the owner of a condominium apartment has free and clear title to the dwelling, owners of cooperative apartments have shares in a corporation that owns a building and leases apartments to them.
(A) While the owner of a condominium apartment has free and clear title to the dwelling,
(B) The owner of a condominium apartment has free and clear title to the dwelling, but
(C) Whereas owners of condominium apartments have free and clear title to their dwellings,
(D) An owner of a condominium apartment has free and clear title to the dwelling, whereas
(E) Condominium apartment owners have a title to their dwelling that is free and clear, while
答案是C。感觉前面的their是说那些 owners of condominium apartments，而后面的them是说owners of cooperative apartments。不是指代同一个对象啊？难道代词指代的对象，只要是张德一样就可以啦（都是owners)？不要管具体的逻辑意思？
谢谢指教！
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