What is the role of the renal system?

The renal system, also known as the urinary system, primarily serves the essential function of filtering waste products from the blood and regulating the body's fluid balance. This includes the removal of substances such as urea, toxins, and excess salts, which are excreted in the urine.

Additionally, the renal system plays a crucial role in maintaining the body's electrolyte balance and pH level, which are vital for overall homeostasis. The kidneys, a key component of the renal system, ensure that the right amount of water is retained or excreted, depending on the body's needs, thus contributing to fluid regulation.

While the renal system does produce hormones and aids in red blood cell production, these are secondary functions. Its primary and most vital roles revolve around waste filtration and fluid regulation, making option B the most accurate representation of its main functions.