African Lungfish, Which Are Often Found in Small, Stagnant Pools

African lungfish, which are often found in small, stagnant pools of freshwater, produce urea as a nitrogenous waste. What is the advantage of this adaptation?

A) Urea forms an insoluble precipitate.
B) Urea makes lungfish tissue hypoosmotic to the pool.
C) The highly toxic urea makes the pool uninhabitable to potential competitors.
D) Small, stagnant pools do not provide enough water to dilute the toxic ammonia.
E) Urea takes less energy to synthesize than ammonia.