The two sentences that contain an example of contested usage are:
- The chair for the chair of the board of directors is at the head of the board table.
- The postman needs to know who this letter is addressed to so it can be delivered.
The first one is contested due to the use of "chair" both as a noun to refer to the person (chairperson) and as a position title, creating potential confusion. The second one is often contested due to the use of "who" instead of "whom" in the context of the sentence.