<prompt> True about cardiac 02 demand isDirectly propoional to mean aerial pressureInversely propoional to hea rateInversely propoional to cardiac workHas a constant relation to the external work done by the hea  <response>: Experimental studies have shown that oxygen consumption of the hea and the chemical energy expended during contraction are directly related to the external work Ref: Guyton and Hall Textbook of Medical Physiology 12th Edn page No:209 