In order to estimate the value of x-y where x and y are real numbers with x>y>0, Xiaoli rounded x up by a small amount, rounded y down by the same amount, and then subtracted her rounded values. Which of the following statements is necessarily correct?
Answer Choices
A. Her estimate is larger than x-y.
B. Her estimate is smaller than x-y.
C. Her estimate equals x-y.
D. Her estimate equals y-x.
E. Her estimate is 0.