There are three boxes. One box has two white balls; one box has two black balls; and one box has one white ball and one black ball. Three labels are attached to the boxes: WW (White and White); BB (Black and Black); and BW (Black and White). Unfortunately, each box is labeled with an incorrect label. You are allowed to open only one box, pick one ball at random, see its color, and put it back into the box without seeing the color of the other ball. Which box should you open to fix the labeling of the three boxes? Explain your answer.