SPOT THE ERROR:Meredith remembered to turn off the lights and lock the door before she left an apartment.

Explanation

"An" is incorrect. The correct phrase should be "left the apartment" instead of "left an apartment," assuming the sentence refers to a specific apartment known to both the speaker and listener. There is an error here.The error in the sentence is the use of "an" before "apartment." The correct phrase should be "left the apartment" to refer to a specific apartment. Thus, the correct option to mark the error is D) An.