Answer:
The correct answer is option - b. protein.
Explanation:
Proteins are expressed in terms of kilogram body weight and are dependent on the quality of it. Bodyweight would be essential to change the EAR for the protein into grams on a daily basis to set a reference value for nutrition.
The other options have a fixed nutrition need in comparison to young adults. Iron, vitamin, and folate have a higher need than the protein in infants.
Thus, the correct answer is option - B.