Which of the following is an example of a reason why firms might pay efficiency wages ?

A. At equilibrium wages workers sleep when the boss is not looking because workers are not deeply concerned about being fired

B. At equilibrium wages workers often quit to find better jobs.

D. At equilibrium wages, workers cannot afford a healthy diet so they fall asleep at work due to a lack of energy

E. At equilibrium wages only minimally qualified workers apply for the job