Answer:
B.John should make sure he trains the workers better, including how to fix the machine.
Explanation:
John is a person who is in an important position in the firm. He must consider the opinion of his workers. It could be useful for him, to accept other opinions and find the best solution for the problem. The readers can see that the problem is repeating and workers want to be sold so they can work undisturbed. This problem can be repeating, so John can take time to train the workers to solve the problem alone. He must fix the machine, but also to explain to the workers how to fix the machine without him.