Humans are particularly susceptible to the effects of undernutrition during periods of rapid growth, such as during

Well I mean Pregnancy which is why i believe that pregnant women eat a lt to combatant the malnutrition?

Undernutrition can be experienced at all stages of development,including during the prenatal growth, infancy and early childhood. They represent the periodsduring which the developing child's system is highly sensitive to malnutrition. This is  because the first years of life witness the most rapid growth. The first 1,000 days have the most rapid changes occur. During Pregnancy if a mother is malnourished so will her unborn child. 

Ithink the answer is 1. warmth

The answer would be a (carbohydrates)