Answer:
C. Plan a schedule
Explanation:
Judge the validity of each answer, and the right one pops out:
A. Supervisors secure adequate customers?
.... not really. They supervise employees in their own company. This role is more outward looking (customers are not part of the supervisor's company).
B. Supervisors develop funding options?
.... well, they might. But this answer is also outward looking. So far, both A and B seem to not fit.
C. Supervisors plan a schedule?
.... someone has to! And others would likely follow the schedule. So far, C is better than either A or B.
D. Supervisors sell the product?
... well, they could, of course, but the employees that do that have a different title: sales people.
Once you go through all the options, C stands out as the best.
