D! and iou not is a document recording a debt and informal agreement, though it can be to do something it is not negotiable to be transferred into payment
The correct answer should be Adams' equity theory.
According to this theory, employees want to be equal at work, especially if they produce the same amount of work. So, if Bob and Tom do the same work, obviously they want to have equal paycheck as the other one, which is why Bob is unhappy because Tom's wage is higher.
With the invention of the stethoscope, physicians were able to listen to the various sounds made by the heart and lungs. And began to be able to identify if patients had any diseases or ailments.