The loops of Henle in the kidneys of a desert kangaroo rat are much longer than those in a white laboratory rat because the __________.

• A. white rat's diet is much less varied than the kangaroo rat's diet
• B. kangaroo rat cannot always find food
• C. kangaroo rat produces more body wastes
• D. kangaroo rat has less stress and lower blood pressure
• E. kangaroo rat is adapted to living in an environment where water is scarce