TACHS Language › Case
Select from the given options the one that includes a usage error. If all of the options are correct, select "no mistakes."
I have no clear idea who I am speaking to.
Excuse me, could you say that again?
Listen, I'm reaching the limits of my patience.
No mistakes
The correct choice features a very common error of pronoun case, which leads the sentence to incorrectly conclude with a preposition. Rather than using the subjective-case "who" in saying "who I am speaking to," it is correct to use the objective-case "whom." Sentences should never, in academic writing, end with a preposition.