The best answer is B.
With a box and whisker plot, 25% of the data goes from the leftmost point to the beginning of the box. The next 25% goes from the beginning of the box to the median, which is represented by the line in the box. The third 25% goes from the median to the end of the box, and the last 25% goes from the end of the box to the end of the line.
The middle 50% is the data within the box.
