Final answer:
The ability to upgrade a classic roll to a signature roll typically depends on the establishment's policy, suggesting that it may be possible with an additional cost if substitutions are allowed.
Step-by-step explanation:
The ability for customers to upgrade from a classic roll to a signature roll at an additional cost suggests a business policy question. Such policies vary by establishment. If the policy states that substitutions are allowed with an additional charge, then the answer would be Yes, with an additional cost. However, without specific knowledge of the establishment's policy, a definitive answer cannot be given. In reality, these policies can sometimes be dependent on availability or might be allowed only on special days, as hinted by the other choices provided (C and D).