Square A B C D has area 36 , and \overline{A B} is parallel to the x-axis. Vertices A, B, and C are on the graphs of y=\log _{a} x, y=2 \log _{a} x, and y=3 \log _{a} x, respectively. What is a ?
Answer Choices
A. \sqrt[6]{3}
B. \sqrt{3}
C. \sqrt[3]{6}
D. \sqrt{6}
E. 6