<prompt> A substance is present in a concentration of 2 mg in the afferent aeriole and zero mg in the efferent. True about the substance is:It is freely filtered at the glomerulusSecreted in coical nephronAbsorbed in PCTImpermeable in the loop of Henle  <response>: This is only a hypothetical situation. Filtration fraction is about 20. It means, of the total plasma passing through the glomerulus per unit time, about 20 is filtered out. If a substance has zero concentration in the efferent aeriole, it means all of that substance was freely and completely filtered out in the plasma that has formed the Glomerular Filtrate. 