Relative Pronoun & Pronoun Ambiguity

[Optimus Prime]

Jack is a friend of Jim, who is a friend of Jerry.

Does this sentence have pronoun ambiguity?

Will a relative pronoun (who,which, where) always refer to the noun just before the comma?

[grockit_andrea]

On the GMAT, a modifier is presumed to modify the word to which it's closest. Here, that's "Jim," so the modifying phrase that begins with "who" is describing Jim. I think that would be pretty standard for relative pronouns introducing modifying phrases, but I can't say that will ALWAYS be the case. I can imagine some scenarios in which a relative pronoun could be more ambiguous, but I can't recall ever eliminating an answer choice because of an ambiguous relative pronoun.