The statement that best refutes the opposing argument is:
D. Shorter school day would allow more students to hold down jobs during the school year rather than just during the summer.
This statement is true because it suggests that even with a longer school year, students could still gain valuable work experience by having more time available each day for part-time jobs.
So, the answer is: D. True.
The evaluations of the other statements are: A. False. B. False. C. False.