Based on the given box plots, the most appropriate comparison of the centers is:
OD. The median for town A, 30°, is less than the median for town B, 40°.
In the box plot for town A, the box extends from approximately 15° to 35°, with the median marked at around 30°. On the other hand, in the box plot for town B, the box extends from approximately 20° to 45°, with the median marked at around 40°. Since the median for town B is higher than the median for town A, statement OD is the correct comparison.