Correct answer is (d) Friends
To explain I would say: The enzyme company will not be in contact with the customer through friends. But they can be in contact with customers through the following individuals:
• Salespeople: ensures that the supply continues and that the cost is mutually acceptable to both.
• Technical salespeople and managers: ensures that their product is performing up to specification and often leads to suggestions for the improvement of the process. They have to deal with the problems to do with the enzyme and should able to solve it themselves or may require the services of the third group, the laboratory or pilot plant scientists.
• Laboratory and pilot plant scientists: will spend some time trouble-shooting as and when necessary.