Concept:Filtration in the kidney moves both useful substances and wastes from the blood into the renal tubule.Explanation:In the glomerulus, blood pressure forces water, useful substances, and wastes out of the blood into Bowman's capsule.This process is called filtration or ultrafiltration.Useful substances are later reabsorbed by selective absorption, but the initial removal is by filtration.Answer:A. Filtration