This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrine System, Subject name: Physiology
Following is/are physiological effects of thyroid hormones on the hea: 
Select and explain. 
A. Increased number of beta adrenergic receptors, B. Blunted response to circulating catecholamines, C. Increased propoion of beta myosin heavy chain, D. All of the above
A: Increased number of beta adrenergic receptors
Answer: A: Increased number of beta adrenergic receptors 
Explanation: None