The kidneys secrete 3 different types of hormones; erythropoietin, renin, and calcitriol (1,25- dihydroxycholecalciferol). Erythropoietin and renin are peptide hormones secreted by the juxtaglomerular cells of the kidney. Calcitriol is a steroid hormone synthesized by the cells of the proximal tubules of the nephrons. The renin secreted has enzymatic activity and is an important part of the renin-angiotensin-aldosterone system (RAAS). The RAAS plays an important role in regulating the cardiac output and arterial pressure. Thus the correct answer is option D.