―How long do you think it is ________ he arrived here?

―No more than half a year, I believe.

　　A. when　　　　 B. that　　　　　C. before　　　　D. since

---How long do you think it is ________ he arrived here?

---No more than half a year, I believe．

1. A.
   when
2. B.
   that
3. C.
   before
4. D.
   since

---How long do you think it is ______ he arrived here?
---No more than half a year, I believe.

1. A.
   when
2. B.
   that
3. C.
   before
4. D.
   since

—How long do you think it is ________ he arrived here? —No more than half a year, I believe.

A. when           B. that　       C. before       D. since

--- How long do you think it is        he arrived here?

    --- No more than half a year, I believe.

       A．when B．that   C．before      D．since