if x+y+z =1. then xy+yz+zx is  Pick one
A) 1 / 2 B) 1 / 3 C) 1 / 4 D) 1 / 5 E) 1 / 6

Rationale: 1 / 2 + 1 / 2 + 0 = 1 xy = 1 / 2 * 1 / 2 = 1 / 4 answer : c
Answer: C