What is true of the x-coordinates of B and B' when reflecting across the line y=-1?

OA. They are the same.

OB. The x-coordinate for B' is the negative reciprocal of the x-coordinate for B.

OC. The x-coordinate for B' is the reciprocal of the x-coordinate for B.

OD. The x-coordinate for B' is the opposite of the x-coordinate for B.