What is the primary function of red blood cells?

Correct Answer: B

Rationale: The primary function of red blood cells, also known as erythrocytes, is to transport oxygen from the lungs to the body's tissues and organs. This is essential for cellular respiration and overall body functions. Red blood cells do not play a role in clotting blood, fighting infection, or carrying hormones. Choice A is incorrect because clotting blood is primarily done by platelets and other components of blood. Choice C is incorrect as fighting infection is a function mainly carried out by white blood cells. Choice D is incorrect because carrying hormones is primarily attributed to proteins like albumin and specific hormone-carrying proteins.

Correct Answer: B

Rationale: The correct answer is B: Absorbing water and forming solid waste. The large intestine plays a crucial role in absorbing water from the remaining indigestible food matter and forming solid waste (feces) to be excreted from the body. This process helps in maintaining the body's fluid balance and eliminating waste efficiently. Choices A, C, and D are incorrect because the large intestine is not primarily responsible for absorbing nutrients, breaking down fats, or secreting digestive enzymes. These functions are mainly carried out in the small intestine.

Correct Answer: B

Rationale: The primary function of the kidneys in the urinary system is to filter blood to remove waste products and excess fluids, which are then excreted as urine. Kidneys act as a filtration system, removing waste like urea, excess salts, and toxins. While the kidneys do play a role in regulating blood pressure by secreting renin and maintaining electrolyte balance by adjusting the levels of sodium, potassium, and other ions in the blood, their main and essential function is filtration and waste removal, making choice B the correct answer.

Correct Answer: B

Rationale: The correct answer is B: 'To break down food.' The stomach plays a crucial role in the digestive system by breaking down food using gastric acid and digestive enzymes. This process transforms the food into a semi-liquid mixture known as chyme, which is further digested in the small intestine. Choices A, C, and D are incorrect because the stomach does not primarily absorb nutrients, produce bile, or store waste. These functions are carried out by other organs in the digestive system such as the small intestine, liver, and large intestine, respectively.

Correct Answer: B

Rationale: The primary function of the immune system is to fight infections. It identifies and destroys pathogens like bacteria and viruses, protecting the body from harmful substances. While oxygen transportation is carried out by the respiratory system, energy production is mainly the role of the metabolic system, and body temperature regulation is managed by the thermoregulatory system. These functions are separate from the immune system's primary role of defending the body against infections.