Problem Solving
试题详情
题目：
Let ∇ denote a mathematical operation. Is it true that x∇y = y∇x for all x and y?
(1) x∇y = 1x + 1y
(2) x∇y = x − y
(1) x∇y = 1x + 1y
(2) x∇y = x − y
选项:
A、A. if statement (1) ALONE is sufficient to answer the question but statement (2) alone is not sufficient;
B、B. if statement (2) ALONE is sufficient to answer the question but statement (1) alone is not sufficient;
C、C. if the two statements TAKEN TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient;
D、D. if EACH statement ALONE is sufficient to answer the question;
E、E. if the two statements TAKEN TOGETHER are still NOT sufficient to answer the question.
答案:
D
