Answer:
D. Mr. Roland’s class was more successful because his class’s lower quartile was the same as Mrs. Cai’s class’s upper quartile.
Explanation:
Mrs. Cai's class's box ranges from 2 to 4, that is, her class’s upper quartile is 4.
Mr. Roland's class's box ranges from 4 to 7, that is, his class’s lower quartile 4.