A) nutrients are found in sinks.
B) fluxes are the pathways of net gain or loss of nutrients.
C) the cycle must be in equilibrium.
D) the boundaries of the ecosystem are not defined.
E) none of the above

A) photosynthesis always balances respiration.
B) CO₂ enters the ocean primarily by photosynthesis.
C) CO₂ in the ocean forms a weak acid.
D) carbon enters the food chain in the form of CO₃^-2.
E) none of the above

A) is the product of respiration and photosynthesis.
B) can be accomplished by most plants.
C) requires energy to break the triple bond in N₂.
D) occurs when nitrate is converted to nitrite.
E) none of the above