Direction: In the following question, a sentence is given divided into four parts (A), (B), (C) and (D). The error, if any, will only be in one part of the sentence. Choose the option with the part containing the error and mark it as your answer. If the sentence is free from errors, mark 'No error' as your answer.

Yesterday, he was (A)/ completing his assignment (B)/ whereas talking to her (C)/ friend over the phone. (D)