A simple way to see this is to ask what question each activity answers. Before a plant can tell workers when to start a job, it must first know which machines and which sequence of operations the job needs, that is routing. Once the path is fixed, the department can slot in start and finish times for each stage, that is scheduling. Only after times are fixed can paperwork and work orders be released to the shop floor to actually begin the job, that is dispatching. Once work is running, someone has to track it and chase up delays, that is follow up. Reading this chain end to end gives Routing, then Scheduling, then Dispatching, then Follow up, matching option 3.
