The relationship between use of new carton & reducing damage is what to evaluate.
(A) Whether BigShoppe dispatchers habitually send out damaged fruits and vegetables to customers
Irrelevant, because the argument focus on transportation, not dispatcher.
(B) Whether the transportation companies used by BigShoppe will handle the new cartons carefully
Correct. If the transportation do not handle new cartons carefully, then customers would still receive damaged products and ask for refunds.(C) Whether the percentage of refunds that BigShoppe makes is higher than those seen by other online shopping companies
Irrelevant. The goal is to reduce refund cost rather than competing them to other companies.
(D) Whether some customers are themselves responsible for the damage caused to the produce
Not quite relevant. Although customers themselves could be responsible for product, the argument specifically attribute the damage to "transportation". So, eliminated.
(E) Whether fruits and vegetables are more vulnerable to incurring damage during shipping than are other fragile products.
Irrelevant. The argument does not dive into which fruits and vegetables are more vulnerable than others.