Urine formation is involved in water and electrolyte balance in vertebrates. Which of the following statements is the most correct regarding urine formation?

A) The formation of the pre- urine is selective.
B) Water is actively pumped across cell membranes to create osmotic gradients.
C) Reabsorption is highly selective so that only ions that are needed are reabsorbed.
D) The Malpighian tubules form the pre- urine.