[USER (data scientist)]: Finally, I plan to conduct a linear regression for each type of surface to identify any trends. Additionally, could you provide an answer to my question: On which surface, how did the win/loss ratio change significantly on each surface from 2012 to 2013?

A. hard, increased,
B. clay, decreased,
C. hard, decreased,
D. clay, increased
E. None of above

[YOU (AI assistant)]: