--You must phone us every week.

--Yes, I _____.

A. must      B. have to         C. will         D. should

--You must phone us every week.

--Yes, I ________.

[　　]

--You must phone us every week.

--Yes, I ________.

[　　]

 - You must phone us every week.
　 - Yes, I _____.
   A. must         B. have to         C. will         D. should