The sentences that contain an example of contested usage are:
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"The chair for the chair of the board of directors is at the head of the board table." (Contested usage of "chair" as a gender-neutral term vs. traditional usage of "chairman.")
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"The postman needs to know who this letter is addressed to so it can be delivered." (Contested usage of "who" vs. "whom.")
(Note: The repetition of the sentences in your response does not change their context, assuming the original intention was to present unique sentences.)