work on
  對…起作用,對…發生影響,從事于…,致力于…
  work on
       v 1: to exert effort in order to do, make, or perform something;
            "the child worked at the multiplication table until she
            had it down cold" [syn: work at]
       2: shape, form, or improve a material; "work stone into tools";
          "process iron"; "work the metal" [syn: work, process]