Final answer:
The data needed to measure the reduction in the time required for James to begin work when told to do so would be option C). Latency.
Step-by-step explanation:
Latency refers to the amount of time that passes between the onset of a stimulus (in this case, the instruction to start work) and the initiation of the student's response (James beginning his work).
This type of data is particularly relevant in the context of applied behavior analysis (ABA) where an RBT (Registered Behavior Technician) is working to improve a client's response times to certain prompts or instructions.
In the context of the other provided information, duration refers to the length of time an event lasts, frequency refers to how often an event occurs, and latency measures how long it takes for an event to start after a prompt.
When working with behavior modification, it's crucial to understand and differentiate between these terms to properly record and analyze data.