Explanation:

- Option 1: Fats

Fats are essential for various body functions but not directly involved in forming hemoglobin. They provide energy and support cell membranes.

- Option 2: Iron

Iron is the critical component for hemoglobin formation. It binds oxygen in the blood and transports it throughout the body, enabling red blood cells to function effectively.

- Option 3: Calcium

Calcium is vital for bone health and muscle function but does not directly participate in hemoglobin production.

- Option 4: Protein

Proteins are essential for overall bodily health and serve as building blocks for muscles, but iron is the specific mineral required for making hemoglobin.