Final answer:
A baby's weight gain from 9 pounds at birth to 40 pounds after 5 years mainly comes from the intake of food and nutrients, which contribute to the development of new cells, muscle tissue, and bones. Continuous monitoring of the baby's growth ensures a healthy progression, with regular doctor visits essential to assess normal growth patterns.
Step-by-step explanation:
Understanding Weight Gain in Children
When a baby is born weighing 9 pounds and then grows to weigh 40 pounds after 5 years, the mass gained comes primarily from A) food and nutrients. This process is a natural part of physical development, wherein the baby’s body uses the nutrients from food to build more body tissue, leading to weight gain. Throughout early childhood, as babies and toddlers consume food, their bodies convert these nutrients into new cells, muscle tissue, and bones. Babies also accumulate fat for energy storage and insulation. A baby’s initial birth weight is influenced by factors such as fetal growth rate and gestational age. After birth, babies typically lose a small amount of weight, but then start gaining it back, usually doubling their birth weight by around six months and tripling it by 12 months.A baby’s first year is crucial for growth as they gain an average of about 1 ounce per day during the first two months and then about 1 pound per month for the rest of the first year. This rate of growth can be affected by various factors, including genetics, nutrition, and overall health. Therefore, continuous monitoring and assessment during doctor visits ensure that the baby is growing normally. Exercise can contribute to a healthy increase in mass, specifically through muscle development. However, the key contributor to a baby’s weight gain over several years is the intake of nutrients rather than exercise alone. There is no "magic" involved in a child’s growth; it is a biological process driven by adequate nutrition and general health.