The answer is school C. A u-shaped distribution would have to have values that when plotted, make a "u". In this case, the first and last values have to be the highest, the second and fourth values have to be in the "middle" and the third value has to be at the bottom. This is the case for school C.
Having a U-shaped distribution means that the school would have the least number in the middle value/values and the most at the ends.
School C exhibits this trend because it has the most on the outermost ranges (82 for between 1.5 and 2, and 78 for between 3.5 and 4.0), as well as the least number for the middle value (26 for 2.5-3.0
The numbers inbetween also follow the trend, as you can see if you read down the column of school C, the numbers decrease as you get to 2.5-3.0 and increase again to 4.0
