The stomach can expand up to eighty times its empty volume partly due to _______ in its walls.

A. Proximal convoluted tubule: The PCT reabsorbs the majority of filtered water and solutes (≈65% Na⁺/H₂O, all filtered glucose and amino acids, many ions).
B. Efferent arteriole: An efferent arteriole is a blood vessel leaving the glomerulus (carries blood), not a tubular segment that reabsorbs filtrate.
C. Afferent arteriole: Afferent arteriole supplies blood to the glomerulus; it is not involved in tubular reabsorption.
D. Loop of Henle: The loop helps concentrate urine (water reabsorption in the descending limb, ion transport in the ascending limb) but the PCT is the primary site for bulk reabsorption.

A. Regulating body temperature of the testes:Correct -the scrotum suspends the testes and adjusts their position to keep testicular temperature slightly below core body temperature, which is necessary for optimal sperm production.
B. Storing urine:Incorrect -urine is stored in the urinary bladder, not in the scrotum.
C. Producing sperm: Incorrect -sperm are produced in the seminiferous tubules inside the testes; the scrotum is a protective/powerful thermoregulatory sac, not the sperm-producing tissue.
D. Carrying sperm to the urethra: Incorrect -ducts such as the vas (ductus) deferens carry sperm toward the urethra; the scrotum does not transport sperm.