Final answer:
The predetermined overhead rate of 120 at Jones Company cannot be determined without additional context. Typically, such rates in job-order costing systems are expressed per unit of a base, but the exact base for the 120 is not provided in the question.
Step-by-step explanation:
The student's question, "Jones Company uses a job-order costing system with a predetermined overhead rate of 120. What is the predetermined overhead rate?", does not provide enough context to determine what the 120 refers to. However, in job-order costing, the predetermined overhead rate is usually expressed in terms of a rate per unit of a base such as direct labor hours, machine hours, or units of production. Without additional information, we cannot accurately select from the provided options whether it is $120 per unit of activity, $120 per direct labor hour, $120 per machine hour, or $120 per unit of production.