If You Look at a Sheet of White Paper in a Dim

If you look at a sheet of white paper in a dim room and then look at it in bright sunlight,the paper will reflect more light to the eye when you are outside than inside.Yet we see the paper as having the same lightness in both situations.Why?

A) The brain adjusts for our memory of the lightness of the paper.
B) The brain makes the assumption that lightness does not change with location.
C) The brain uses the paper/surround intensity ratio in both locations.
D) The brain adjusts the perception of the lightness of the paper.