With regard to stress and disease,​

A) ​executives are more likely than middle-level managers are to develop diseases associated with stress.
B) ​stress can affect disease development directly through the immune system or indirectly through behaviors.
C) ​stress is more likely to result in psychological disorders than it is to result in physiological diseases.
D) ​both a and c are correct.

Research has shown that stress can affect disease development both directly through the immune system and indirectly through behaviors such as poor diet and lack of exercise. There is no evidence to support the claim that executives are more prone to stress-related diseases, and stress has been linked to both physiological and psychological disorders. Therefore, option B is the most accurate statement.