The two sentences that contain an example of contested usage are:
- "The postman needs to know who this letter is addressed to so it can be delivered."
- "The chair for the chair of the board of directors is at the head of the board table."
The term "who this letter is addressed to" raises a contested usage issue related to preposition placement at the end of sentences. Additionally, "chair" can be contested as it refers to a position (the chair of the board) and might be confused with physical furniture, creating ambiguity.