Final answer:
Meat and some plant products like legumes are the major food sources of urea since they are high in proteins, which are broken down to form urea. The kidneys filter this urea from the blood, which is then excreted in urine.
Step-by-step explanation:
The food source that provides the majority of the urea that is filtered from the blood via the kidneys is A. Meat and some plant products such as legumes. Urea is a nitrogen-containing molecule that is formed when foods containing protein are broken down in the body. Protein-rich foods, including meat, poultry, and certain plant products like legumes, significantly contribute to the production of urea. This urea is then carried in the bloodstream to the kidneys, where it is filtered out and excreted in the urine.
Patients with kidney diseases may need to rely on dialysis machines to remove the harmful urea from their blood, which demonstrates the crucial role of the kidneys in managing urea levels in the body. Furthermore, high protein diets, particularly non-vegetarian diets, can lead to increased urea production, while conditions like kidney dysfunction can impair the elimination of urea, leading to toxic levels.