For each pair of sentences, give the most general unifier if it exists. If it doesn't, explain why. Note that all uppercase letters are constants and all lowercase letters are variables. A. P(A, B, B) P(x, y, z) B. Ply, G( A, B )) PC G(x,x), y) C. P( F(x), x) P( F(y), A) D. P( F(A), A, z) P( F(x), y, G(B)) E. P(A, B) Q(x, B )