Note that the x -coordinate always comes first. The x -coordinate of point B is 100. The y -coordinate of point B is 400. The y -coordinate of point D is 100. If a point is lying on an axis, you do not need to draw lines to determine the coordinates of the point.
C lies on the x -axis.
When a point lies on an axis, one of its coordinates must be zero. If you look at how far the point is from the origin along the x -axis, the answer is zero. Therefore, the x -coordinate is zero. If you look at how far the point is from the origin along the y -axis, the answer is zero. Therefore, the y -coordinate is zero.