Qingtian weather

Find the temperature difference of four days, and then compare the sizes; According to the chart, the temperature difference on 12 is17-11= 6℃; The temperature difference on 14 is 20-12 = 8℃; The temperature difference on 16 is14-11= 3℃; The temperature difference on 18 is 24-15 = 9℃;

So the maximum temperature difference is 18.

Therefore, choose: d.