Two hormones working on the regulation of water balance that directly oppose each other include

The two hormones are ANP (atrial natriuretic peptide) and aldosterone.  

The aldosterone from the adrenal gland functions on the kidney to encourage reabsorption of sodium, thus, inhibiting its loss in the urine. On the other hand, the ANP or ANF (atrial natriuretic factor) refers to a peptide hormone that minimizes the volume of expanded extracellular fluid by enhancing renal sodium secretion.  

It is produced and secreted by cardiac muscle cells in the walls of the atria in the heart. The hormone functions on the kidney to encourage excretion of sodium so that it is excreted in the urine.  

b is the correct answer