Directions: The following question has a sentence with three parts labelled (a), (b) and (c). Read the sentence to find out whether there is any error in any part and indicate the letter of that part as your answer. If you find no error, your answer should be indicated as (d).

(a) Since the attachment of air-conditioned sleeping car to all important trains, (b) travelling become very pleasant (c) especially during the summer season. (d) No error