Final answer:
The 10-month-old switched from formula to whole milk is at the greatest risk for iron deficiency anemia because whole milk is a poor source of iron, and infants have high iron demands.
Step-by-step explanation:
The child at greatest risk for iron deficiency anemia among the options provided is the 10-month-old who has been switched from formula to whole milk. This is because, while human milk and transitional formulas are typically fortified with iron to meet the needs of a developing infant, whole milk is a poor source of iron. This, combined with the fact that infants have increased iron demands due to rapid growth, puts the 10-month-old who is no longer receiving iron-fortified formula at a higher risk for iron deficiency anemia.
A 4-month-old term infant exclusively fed human milk would not be at the highest risk because human milk contains a small amount of highly bioavailable iron. A 4-month corrected gestational age, former preemie on a transitional formula is typically provided with an iron-supplemented diet to account for poor stores at birth. Lastly, the 17-month-old 'picky eater', while also at risk for iron deficiency anemia, is less likely to be at the greatest risk unless their diet lacks appropriate iron-rich foods entirely.