请教一道manhattan SC 6th 第四章的题，关于that和which

原句5. People that are well-informed know that Bordeaux is a French region whose most famousis the wine which bears its name.

答案：Well-informed people know that Bordeaux is a French region whose most famous export is the wine that bears its name.

解析：that are well-informed: INCORRECT. This clause uses the relative pronoun that to refer topeople. Who must refer to human beings. Another problem with that are well-in-formed is that it is wordy. Avoid relative clauses whose only verb is a form of to be,because they can generally be expressed more succinctly.
               whose most famous...bears its name: CORRECT. This clause modifies region. Notice that whose, unlike who and whom, can correctly modify non-human entities.
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which bears its name: INCORRECT. The context of this sentence calls for an essential clauseto modify the wine, since the point of the clause is to identify the wine. If the sentence ended with the wine, it would be incomplete. The clause should therefore begin with that rather than which.
请问为什么这里用that不用which呢？迷茫中@-@