单选题 Is -3 < x < 3 ?(1) x2 + y2 = 9(2) x2 + y<9

A、 Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B、 Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C、 BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D、 EACH statement ALONE is sufficient.
E、 Statements (1) and (2) TOGETHER are NOT sufficient.

【正确答案】 A

【答案解析】(1) Given that x2 +y2 = 9，If x< -3 or if x > 3, then x2 > 9 and y 2 < 0, which is not possible. Therefore, -3 < x < 3; SUFFICIENT.(2) Given that x2+y<9, if x = 0 and y = 4, then x2 +y <9, and -3 ≤x ≤ 3 is true. However, if x = 4 and y = -7, then x2 +y ≤ 9, and -3 ≤ x ≤ 3 is not true; NOT sufficient.The correct answer is A; statement 1 alone is sufficient.