ANSWER
[tex]c)(-7,5)[/tex]EXPLANATION
We want to find the coordinates of the vector after the rotation.
For 90 degrees counter-clockwise rotation, the rotation rule is:
[tex](x,y)\to(-y,x)[/tex]Therefore, for the given vector:
[tex](5,7)[/tex]it becomes:
[tex](-7,5)[/tex]The answer is option C.