Correct Option: D

Ecological productivity refers to the primary fixation of solar energy by plants and the subsequent use of that fixed energy by plant-eating herbivores, animal-eating carnivores, and the detritivores that feed upon dead biomass. Ecologists refer to the productivity of green plants as primary productivity. Deserts, tundra, and the deep ocean are the least productive ecosystems, typically having an energy fixation of less than 0.5 × 10³ kilocalories per square meter per year (thousands of kcal/m²/yr; it takes one calorie to raise the temperature of one gram of water by 34°F [1°C] under standard conditions, and there are 1,000 calories in a kcal). Grasslands, montane and boreal forests, waters of the continental shelf, and rough agriculture typically have productivities of 0.5-3.0 × 10³ kcal/m²/yr. Moist forests, moist prairies, shallow lakes, and typical agricultural systems have productivities of 3-10 × 10³ kcal/m²/yr. The most productive ecosystems are fertile estuaries and marshes, coral reefs, terrestrial vegetation on moist alluvial deposits, and intensive agriculture, which can have productivities of 10-25 × 10³ kcal/m²/yr.