In statement given below, a part of the sentence is enclosed in quotation marks. Below are given alternatives to the quotes part which may improve the sentence. Choose the correct alternative. In case no improvement is needed, option 'D' is the answer.No sooner "he had returned home then" his mother felt happy.

• A. had he returned home when
• B. he had returned home than
• C. did he return home than
• D. No improvement