<h2>
Answer:</h2>
Option: B is the correct answer.
B) m∠ A'B'C' = m∠ABC
<h2>
Step-by-step explanation:</h2>
We are given coordinates of Point A,B and C as:
A(1,-1) , B(5,-4) and C(1,-4)
Since, on rotating the points 90 degree counterclockwise about the origin the rule that holds for this transformation is:
(x,y) → (-y,x)
Hence,
A(1,-1) → A'(1,-1)
B(5,-4) → B'(4,-5)
C(1,-4) → C'(4,-1)
<em>As we know that the rotation is a rigid transformation that is the shape and size of the figure is preserved.</em>
<em>Also, the angle measure remains the same.</em>
Hence, m∠ABC=m∠A'B'C'