He was told that it would be at least three more months       he could recover and return to work.  [ ]

A. when                        

B. before

C. since                        

D. that

368+（    ）=68+（    ）

486+328+114=328+（    ）+（    ）

857-298=857-300○（    ）

697-203=697-200○（    ）