When a point is rotated 90 degrees clockwise, its coordinates change as follows:
New X-coordinate = Old Y-coordinate
New Y-coordinate = -Old X-coordinate
In this case, the original point is (-3,3). When we rotate it 90 degrees clockwise, the new coordinates become (3,-3).
The new point (3,-3) is located in Quadrant III, where the x-coordinate is positive and the y-coordinate is negative. Therefore, the correct answer is C. quadrant III.