The amount the objective function coefficient of a decision variable would have to improve before that variable would have a positive value in the solution is the

Reduced cost

Explanation:

Reduced cost is the cost that determines about increment and decrements taking place in objective coefficient before optimal solution gets altered.It is also denoted as opportunity cost in terms of linear programming and analysis field.

This coefficient raises up for maximization issue and decreases if minimization issue occurs for improvement prior variable persist a positive value for the optimal solution.

a is the answer because it just is