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 .