zero-based budgeting

A definition of zero?based budgeting is set out below, with two blank sections. “Zero?based budgeting: a method of budgeting which requires each cost element ___________, as though the activities to which the budget relates _______________.” Which combination of two phrases correctly completes the definition? Blank 1 Blank 2 A to be specifically justified could be out?sourced to an external supplier B to be set at zero could be out?sourced to an external supplier C to be specifically justified were being undertaken for the first time D to be set at zero were being undertaken for the first time sir the answer is C. But i am wondering why D is wrong?