―My foot hurts terribly, doctor.
    ―Well, I wonder ______ it has been like this.
A. since when         B. since then
C. how            D. when

--My foot hurts terribly,doctor.

--Well,I wonder _______ it has been like this.

1. A.
   since when
2. B.
   since then
3. C.
   how
4. D.
   when

--My foot hurts terribly,doctor.

--Well,I wonder _______ it has been like this.

[　　]

--My foot hurts terribly,doctor.

--Well,I wonder _______ it has been like this.

[　　]