Concept:Ultrafiltration in the kidney occurs where blood plasma is filtered into the renal tubule system.Explanation:Blood enters the glomerulus, a network of capillaries.The pressure forces fluid and small molecules out of the glomerular blood into the Bowman's capsule.This process is called ultrafiltration.Therefore, the site of ultrafiltration is the Bowman's capsule.Answer:B. Bowman's capsule