The following data sufficiency problems consist of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements plus your knowledge of mathematics and everyday facts (such as the number of days in July or the meaning of counterclockwise), you must indicate whether.
In the figure above, what is the length of WZ ？（） (Note, figure not necessarily drawn to scale.)
(1) xy=64
(2) x2=y2
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.
参考答案：C
解析：
alone is not sufficient, because x and y could be any numbers that multiplied together make 64; remember, you cannot assume that figures are drawn to scale, so (x, y) could be (8, 8) or (1, 64). (2) alone is insufficient, because it gives no information about what x or y equal. The two statements combined are sufficient, because there is only one number that matches the conditions: x=y=8 (you do not have to consider the possibility of negative values here, since the question talks about lengths, and neither x nor y can be a negative length in the figure as drawn).