Answer:
A. AB = xyzx
Step-by-step explanation:
You want AB when A = BC, B = x, and C = yz.
Substitution
You can evaluate the unknown expression by making substitutions until you can't anymore.
AB = (BC)(B) . . . . . . . . substitute BC for A
AB = ((x)(yz))(x) . . . . . . substitute x for B (2 places), yz for C
AB = xyzx . . . . . . . . . . remove the unnecessary parentheses
