Ivan Had an Emergency Appendectomy Performed Last Night

Ivan had an emergency appendectomy performed last night.When he woke up this morning he was surprised to learn that he had control over the amount of pain medication he received because all he had to do was push a button and morphine was added to his IV fluids.The more often he pushed the button,the more pain medication he was receiving.Ivan acted like an average patient in that he actually ended up administering less medication than other patients receiving the dosages from hospital staff.Which of the following best explains this phenomenon?

A) his feeling of being deceived by the hospital staff caused him avoid medication
B) his feeling of control over the pain decreased endorphin release
C) his feeling of control over the pain increased endorphin release
D) his feeling of control over the medication increased desire to conserve it