This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Circulation: Cardiac Output, Venous Return, Subject name: Physiology
Changes in cardiac output is minimal during: 
Select and explain. 
A. Sleep, B. From supine to standing position, C. Exercise, D. Arrhythmias
A: Sleep
Answer: A: Sleep 
Explanation: Ref: Pal GK. Cardiac output. In: Textbook of Medical Physiology. Ahuja Publishing House. 2007; 74: 607.Explanation:Increased cardiac outputExerciseAnxietyEmotion and excitementT environmental temperatureEatingPregnancyDecrease in cardiac outputStanding from supineSweatingNo change in cardiac outputSleepMild to moderate change in environmental temperature