Figure b: a reflection across the y-axisfigure a 180° rotation around the origin

Since I can't see the figure on the coordinate plane, I can't give you exact coordinates for you to plot to get Figure B or Figure C. But I can tell you the transformation rules for reflection across the y-axis and the 180 rotation around the origin. 

Rule for reflection across y-axis
(x, y)  (-x, y)
For example: Point B in a sample figure has the coordinate point of (1,2) would have a point of (-1, 2) when reflected across  the y-axis. 

Rule for rotating 180 degrees 
(x, y)  (-x, -y)
For example: Point C in a sample figure has the coordinate point of (3, 4) would have a point of (-3, -4) when rotating 180 degrees around the origin.