**Core Concept**
During late pregnancy, the body undergoes significant changes, including increased metabolic rate, blood volume expansion, and fetal growth. As a result, the energy requirement increases to support these processes, ensuring adequate nutrition and fetal development.

**Why the Correct Answer is Right**
The energy requirement in late pregnancy is approximately 300-350 kcal/day above the non-pregnant state, primarily due to the increased metabolic rate and fetal growth. This energy is utilized for fetal growth and development, placental function, and maternal tissue and organ adaptations. The increased energy demand is largely met by an increase in maternal glucose uptake, fat oxidation, and protein synthesis.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as this option does not specify the correct energy requirement increase during late pregnancy.
**Option B:** Incorrect, as this option suggests a much lower energy requirement increase than the actual value.
**Option C:** Incorrect, as this option does not accurately represent the energy requirement increase during late pregnancy.

**Clinical Pearl / High-Yield Fact**
It is essential for pregnant women to consume a balanced diet that meets their increased energy requirements to support fetal growth and development. A diet rich in essential nutrients, including protein, iron, and folic acid, is crucial for a healthy pregnancy.

**Correct Answer: D. 300-350 kcal/day.**