A counterclockwise rotation changes the coordinate of a point as,
(x,y)-->(-y, x).
So, the x coordinate becomes negative of y coordinate and the y coordinate becomes x after transformation.
Let (x,y) be the coordinates of B. Initially the vertex B is in first quadrant with positive coordinates (x,y).
The transformation will give a negative value for the new x coordinate of B only in the first transformation
Hence, the first figure is the answer.
