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).
He explained the matter at great length but I was not the wiser
He explained the matter
at great length
but I was not the wiser
No error.
Correct answer is B
at length