The given sentence has no error.There are some nouns that are singular in a sense but take plural question tag, e.g:- Everyone, each, every, nobody, none, everybody, no one, etc.The pattern of a question tag is: I. Auxiliary (e.g. do, did, is etc.) + not + subject (if the statement is affirmative) II. Auxiliary (e.g. do, did, is, etc.) + subject (if the statement is negative) Hence, the correct option is (D).