—  I really don’t know how to thank you enough.

   —  _____.

A. No problem                                                 B. Think nothing of it         

C. Not at all                                                                D. It doesn’t matter

 ---I really don’t know how to thank you enough.

   ---___________ .

A. No problem.           B. Think nothing of it.   

C. With pleasure.          D. Glad to hear that.

---I really don’t know how to thank you enough.       ---       .

A. No problem  B. Think nothing of it   C. With pleasure.  D. Glad to hear that

—I really don’t know how to thank you enough .

    —       .

       A．No problem           B．Think nothing of it

       C．Not at all         D．It doesn’t matter 

—I really don’t know how to thank you enough .

—       .

A．No problem                                              B．Think nothing of it

C．Not at all                                                   D．It doesn’t matter