$1.$ The graphical method of solving a linear programming problem uses:

A$.$ All points in the feasible region

B$.$ Only the interior points of the feasible region

C$.$ Only the corner points in the feasible region

D$.$ All of the above.

E$.$ Only A and B$.$

F$.$ Only B and C

G$.$ Only the optimal solution.

H$.$ Always uses the maximum value of a corner point in the feasible region.

I. Always uses the minimum value of a corner point in the feasible region.

J$.$ The primary constraint to assess the optimum value.

K$.$ The non$-$negativity constraints to derive the optimal solution.