In this section, there is a sentence with three underlined parts labelled (a), (b), (c). Read the sentence to find out whether there is any error in any underlined part and select your answer from the given options against the corresponding letter i.e., (a) or (b) or (c). If you find no error, your answer should be indicated as (d).
After a successful tour of Europe, my old parents returned back to India on New Year's day. No ERROR.
(a) (b) (c) (d)