Multiple choice Directions: Choose the part in which there is an error: I have written numerous letters to the concerned authorities but nothing has been done so far Reveal answer Fill a bubble to check yourself C Correct answer Explanation Option 3 is where the error lies. There must be a comma (",") at the end because the next part of the sentence begins with the word "but". Whenever you use the word "but" it must be preceded by a comma unless it starts a sentence.