The correct answer is option 2: Urinary bladder. The urinary bladder is a muscular sac located in the pelvis. Its main function is to store urine produced by the kidneys until it is ready to be eliminated from the body. After the kidneys filter the waste products from the blood, urine travels from the kidneys through tubes called ureters and then into the urinary bladder. The urinary bladder expands as it fills with urine, and when it becomes full, it initiates the urge to urinate. At that point, urine is expelled from the body through another tube called the urethra. The kidneys, mentioned in option 1, are responsible for producing urine, but they are not where urine is stored. Options 3 and 4 (Liver and Nephron) are incorrect as they do not play a role in storing urine.