--- When did your father come back last night?

--- He didn’t come back _______ he finished all the work.                                                           

A. until                                  B. while                              C. if                           D. unless

--- When did your father come back last night?
--- He didn’t come back _______ he finished all the work.                                                           

---When did your father come back last night?

---He didn’t come back______ he finished all the work.

1. A.
   until
2. B.
   while
3. C.
   if
4. D.
   that