The 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."
- This sentence contains a contested usage in the phrase "who this letter is addressed to," where some grammarians argue that it should be "to whom this letter is addressed."
-
"Stephanie started reading the book first, and therefore she finished it before I did."
- In this sentence, the use of "therefore" can be seen as contested, as some might argue it does not logically connect the two clauses as intended, depending on the interpretation of the timing.
(Note: The first option is definitely contested due to the use of "who" instead of "whom," while the second's contested nature can depend on interpretation of the logical coherence of the statement.)