Triangle A B C lies in the first quadrant. Points A, B, and C are reflected across the line y=x to points A^{\prime}, B^{\prime}, and C^{\prime}, respectively. Assume that none of the vertices of the triangle lie on the line y=x. Which of the following statements is not always true?

**Answer Choices**

A. Triangle A^{\prime} B^{\prime} C^{\prime} lies in the first quadrant.

B. $Triangles A B C and A^{\prime} B^{\prime} C^{\prime} have the same area.$

C. $The slope of line A A^{\prime} is -1 .$

D. $The slopes of lines A A^{\prime} and C C^{\prime} are the same.$

E. $Lines A B and A^{\prime} B^{\prime} are perpendicular to each other.$