--- Good evening, Professor Hardy. --- Good evening, John. Come in, please. --- Thank you, I hope I am not interrupting you. --- No, ____________.

--- Good evening, Professor Hardy.

--- Good evening, John. Come in, please.

--- Thank you, I hope I am not interrupting you.

--- No, ____________.

A. thank you

B. not at all

C. thanks

D. let it alone