The correct answer is: Lighter objects need greater force than heavier objects to start moving but will accelerate at the same rate.
This argument supports the student's claim because it explains that box 1, which experienced a larger force of 40 N and a greater acceleration of 10 m/s^2, must have a smaller mass. According to Newton's second law of motion, the force applied to an object is directly proportional to its mass times its acceleration (F = ma). Therefore, if the force applied is the same, but the acceleration is larger, the mass of the object must be smaller.