Answer: The answer is (C) (4,1).
Step-by-step explanation: Given points are A(0,3), B(-1,4) and C(2,-1). Obviously, these points will form a triangle. We need to find the co-ordinates of the point B', which is formed after rotating the figure counter-clockwise 90 degrees.
The point B(-1,4) lies in the second quadrant. After rotating 90 degrees counter-clockwise, the this point will lie in the first quadrant. So, both the x-coordinate and y-coordinate will be positive. Also, the two coordinates will exchange. Please see the attached figure.
Thus, the coordinates of point B' are (4,1).
Hence, (C) is the correct option.