In the following question, a part of the sentence is in Bracket . Below are given alternatives to the word in bracket part. Choose the correct alternative which may impove the sentence. In case no improvement is needed our answer will be no improvement. Question I don't understand (why did you not call) me last night.

• A. why had you not call
• B. why you did not call
• C. why not did you call
• D. No Improvement