Which of the following most logically completes the argument?
Nitrogen, an essential nutrient that all plants use to make protein, occurs naturally in the soil and can be supplemented with fertilizer. Even though the corn and tomato plants in Sunshine Farm received the same amount of nitrogen fertilizer, the tomato plants did not produce fruit, while the corn plants thrived. This fact, however, does not mean that the tomato plants’ soil was deficient, because _______.