Read the sentence below to find out whether there is any grammatical error in it. The error, if any, will be in one part of the sentence. Choose the option with that part as your answer. If there is no error, choose 'D' as your answer. (Ignore the errors of punctuation, if any).
Since the attachment of airconditioned sleeping cars to all important trains, travelling became very pleasant, especially during the summer season.
Since the attachment of airconditioned sleeping cars to all important trains,
travelling became very pleasant,
especially during the summer season.
No error
Correct answer is B
travelling has become very pleasant