Final answer:
The most common cause of iron deficiency in infants is dietary deficiency.
Step-by-step explanation:
The most common cause of iron deficiency in infants is dietary deficiency. Infants may not be receiving enough iron in their diet, which can lead to iron deficiency anemia. Iron-rich foods, such as fortified cereals, leafy greens, and lean meats, should be introduced to their diet to prevent iron deficiency.