Final answer:
Raisins contain more iron per calorie than grapes primarily because the dehydration process makes them nutrient-dense with a greater concentration of iron per calorie, not necessarily due to higher natural iron content or fortification methods. The correct option is b) The iron content in grapes is naturally lower.
Step-by-step explanation:
To explain why raisins contain more iron per calorie than grapes, we should consider the process of dehydration that grapes undergo to become raisins.
The water content is significantly reduced, leaving behind a denser product with a greater concentration of nutrients, including iron, per calorie. This is not necessarily related to the raisins having a naturally higher iron content, but rather, they are more concentrated forms of the nutrients found in grapes.
Additionally, the form of iron used to fortify foods, which is often metallic iron due to cost and the lack of impact on taste and other food properties, does not relate directly to the natural iron content of raisins versus grapes. Also, the quantity of consumption or the bioavailability of iron in raisins versus grapes is not the primary reason for the difference in iron content per calorie. The correct option is b) The iron content in grapes is naturally lower.