Which of the following graphs is the level set of F(x. y) = 3y corresponding to z = ? (A) (B) -3 -2 2 3 -2 -1 2 -1 -1 -2 (C) (D) -3 -2 -1 1 2 3 -2 -1 1 2 -1 X -1 X -2 -2 (E) (F) -3 -2 -1 2 -3 -2 -1 1 2 3 -1 -1 -2 (G) (H) -3 -2 2 3 -2 -1 2 -1