The human kidney secretes many hormones: erythropoietin (EPO), calcitriol, vitamin $D _3$, as well as the enzyme renin. The kidneys also produce prostaglandins.

Calcitrol is produced by the cells of the proximal tubule of the nephron in the kidneys. Erythropoietin is also produced by the kidney. Renin is secreted by the juxtaglomerular kidney cells. Angiotensinogen is a component of the renin-angiotensin (RAS) system and is released into circulation mainly by the liver. So, the correct answer is 'Angiotensinogen'. 

Renin is the enzyme secreted by the juxta glomerulus of the kidney to the bloodstream. It regulates the blood pressure by converting the angiotensinogen protein to angiotensin I and then further into the angiotens II

Renin is the enzyme secreted by the kidney. Juxa glomerular cells present in kidney release renin. It activates the renin-angiotensin system and produces a rise in blood pressure.  It has stretch receptors in the vascular walls which sense changes in renal perfusion pressure.

Erythropoietin is a glycoprotein hormone that controls erythropoiesis, or red blood cell production. It is a cytokine (protein signaling molecule) for erythrocyte precursors in the bone marrow.

Erythropoietin is a hormone produced by the kidney that leads to the formation of red blood cells (RBC) in the bone marrow. Its major function is to enable the differentiation and development of red blood cells and to initiate the production of hemoglobin. Thus the correct answer is option A.

A.Cholecystokinin is a hormone which is secreted by cells in the duodenum and stimulates the release of bile into the intestine and the secretion of enzymes by the pancreas.
B.Erythropoietin is a hormone produced primarily by the kidneys. 
C.Secretin,a hormone released into the bloodstream by the duodenum.
So,the correct option is 'Epinephrine'.

• Angiotensinogen is a precursor protein made in the liver for a hormone called angiotensin I. 
• And renin catalyzes a reaction that converts the angiotensinogen protein into angiotensin I, which is a precursor hormone that is converted to an active hormone called angiotensin II by an enzyme known as an angiotensin-converting enzyme in the lungs. Hence, Angiotensinogen is converted to angiotensin by renin.

• Renin, also known as an angiotensinogenase, is an aspartic protease protein.
• This enzyme is secreted by the kidneys that participate in the body's renin–angiotensin–aldosterone system (RAAS)  that mediates the volume of extracellular fluid (blood plasma, lymph and interstitial fluid), and arterial vasoconstriction. 
• Thus, it regulates the body's mean arterial blood pressure. Hence, renin is not secreted by the liver.

• Erythropoietin is a  peptide hormone produced primarily by juxtaglomerular cells of the kidney.
• Erythropoietin stimulates the bone marrow to produce more red blood cells.
• The resulting rise in red cells increases the oxygen-carrying capacity of the blood.
•  As the prime regulator of red cell production, erythropoietin's major functions are to promote the development of red blood cells. Hence, Juxtaglomerular cells of kidney produce a peptide hormone called Erythropoietin.

• Renin is a hormone produced by the juxtaglomerular cells of the kidney.
• Renin also acts as an enzyme in the conversion of angiotensin-1 to its active form, angiotensin-2 involved in constriction of blood vessels. Hence renin is both a hormone and an enzyme. Hence, renin is both a hormone and enzyme.

• Angiotensin is a polypeptide that narrow blood vessels and thus regulates arterial pressure. 
• Angiotensin not only constricts blood vessels all over the body in order to increase systemic blood pressure, but it also works in the kidneys in order to maintain blood pressure in the glomerulus(glomerular pressure) so that the glomerular filtration rate stays normal even in the condition when blood pressure is low. Hence, angiotensin increases glomerular pressure.

• Erythropoietin is a hormone released by the kidney.
  
• It is a glycoprotein. 
• This hormone helps in the proliferation and differentiation of erythrocyte precursors.
• Thus, they produce red blood cells (RBCs) from the bone marrow cells and this process is also known as erythropoiesis.
• The cells of the kidney that produces erythropoietin are sensitive to low oxygen levels in the blood that travels to the kidney.
• So, the correct answer is 'Glycoprotein'.

• Erythropoietin is a hormone released by the kidney.
  
• It is a glycoprotein. 
• This hormone helps in the proliferation and differentiation of erythrocyte precursors.
  
• Thus, they produce red blood cells (RBCs) from the bone marrow cells and this process is also known as erythropoiesis.
  
• The cells of the kidney that produces erythropoietin are sensitive to low oxygen levels in the blood that travels to the kidney.
• The extrarenal site for erythropoietin release is liver.
• So, the correct answer is 'Kidneys'.

Carbon dioxide is transported in the blood from the tissue to the lungs in three ways: (i) dissolved in solution in the plasma; (ii) buffered with bicarbonate (i.e as hydrogen carbonate ions) and (iii) bound to proteins, particularly hemoglobin.  So, the correct option is 'Erythropoietin'.

• Chymase is a chymotrypsin-like serine protease found in the mast cells and also present in basophil granulocytes.
  
• Chymase hydrolyzes chymotryptic substrates by activating chymotrypsinogen.
  
• So, the correct answer is 'Activator of chymotrypsinogen'.