John offered his mother a nice gift on her birthday. John's mother: “Thank you very much for your gift! How wonderful it is!”  John: “______.”

Mark the letter A, B, C or D on your answer sheet to indicate the most suitable response to each of the following exchanges.

John offered his mother a nice gift on her birthday.

John's mother: “Thank you very much for your gift! How wonderful it is!”

 John: “______.”