单选题 Given that x ≠ y and that (x - y)2 = (x + y)2, which of the following must be true?
Ⅰ.x+y=x-y
Ⅱ.y = 0
Ⅲ. xy = 0
  • (A) None
  • (B) Ⅱ only
  • (C) Ⅲ only
  • (D) Ⅰ and Ⅲ
  • (E) Ⅰ, Ⅱ, and Ⅲ


【正确答案】 C
【答案解析】