Which of the following is an example of an amphibian? MCQ with Answer and Explanation

Explanation:
The heart is a muscular pump that circulates blood through the cardiovascular system, delivering oxygen and nutrients to tissues and removing waste. The lungs are the primary organs of the respiratory system, where gas exchange occurs: oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli to be exhaled. The kidneys are the primary excretory organs, filtering blood to remove metabolic waste, excess water, and ions, producing urine. All statements are correct.

Explanation:
Renin is secreted by juxtaglomerular cells of the kidney in response to low blood pressure or sodium. It converts angiotensinogen to angiotensin I, initiating the RAAS. Liver produces angiotensinogen, adrenal aldosterone, heart ANP.

Explanation:
B lymphocytes (B cells) differentiate into plasma cells that produce and secrete antibodies (immunoglobulins) specific to antigens, providing humoral immunity. T cells are involved in cell-mediated immunity. Erythrocytes carry oxygen, platelets clot blood, monocytes differentiate into macrophages that phagocytose pathogens. Lymphocytes are a type of white blood cell.