Under conditions of constant illumination,the compensation period for a whole aquarium would be of infinite length when:

• A
  The biomass of animals equals the biomass of plants
• B
  The respiratory exchanges of the animals are equal to the photosynthetic exchanges of the plants
• C
  The oxygen intake of the animals equals the oxygen output of photosynthesis
• D
  The carbon dioxide output of the animals and plants equals the photosynthetic intake of the plants