<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:An investigator is studying the effect of antihypertensive drugs on cardiac output and renal blood flow. For comparison, a healthy volunteer is given a placebo and a continuous infusion of para-aminohippuric acid PAH to achieve a plasma concentration of 0.02 mgml. His urinary flow rate is 1.5 mlmin and the urinary concentration of PAH is measured to be 8 mgml. His hematocrit is 50. Which of the following values best estimates cardiac output in this volunteer?? A: 3 Lmin, B: 6 Lmin, C: 8 Lmin, D: 1.2 Lmin, E: 4 Lmin,  <response>: This is a physiology question asking about estimating cardiac output based on PAH clearance. PAH is filtered by the glomerulus and secreted into the urine without being reabsorbed. By knowing the urinary flow rate, urinary PAH concentration, and plasma PAH concentration, we can calculate the renal clearance of PAH which equals renal plasma flow. Since renal plasma flow is typically 20-25 of cardiac output, we can estimate cardiac output from renal plasma flow.B: 6 Lmin 