Researchers have studied the cost-effectiveness of growing halophytes -- salt-tolerant plant species -- for animal forage. Halophytes require more water than conventional crops, but can be irrigated with seawater, and pumping seawater into farms near sea level is much cheaper than pumping freshwater from deep wells. Thus, seawater agriculture near sea level should be cost-effective in desert regions although its yields are smaller than traditional, freshwater agriculture. Which one of the following, if true, most strengthens the argument above?
A: Costs other than the costs of irrigation are different for halophytes grown by means of seawater irrigation than for conventional crops.
B: Large research expenditures are needed to develop the strains of halophytes best suited for agricultural purposes.
C: A given volume of halophytes is significantly different in nutritional value for animal forage from the same volume of conventional forage crops.
D: Pumping water for irrigation is proportionally one of the largest costs involved in growing, harvesting, and distributing any forage crop for animals.
Choose A, B, C or D as your solution.
D