C is your answer.
Higher ups should NEVER ignore work, whether from someone in a higher or lower position than them.
He should HELP fix machines, but not by himself.
**explanation for C** He should make sure he trains his workers better and show them how to fix machines. He shouldn't be doing all the fixing and he is probably really busy, or he may be out, who would fix the machines then? The workers would have to.
He should not tell the workers to figure it themselves. They could break it more or lock something up. It is also his job to train them and fix it, and it is incredibly rude to tell them to figure it out themselves.
