**Core Concept**
The size of various organs and structures in the human body at birth is a critical aspect of medical knowledge, particularly for neonatal care. The size of these structures at birth is compared to that of an adult to assess their relative maturity and potential for further growth.

**Why the Correct Answer is Right**
The correct answer is likely to be one of the options that is significantly smaller in size at birth compared to an adult. For example, the **liver** of a newborn is relatively large compared to the rest of their body, but it is still only about 10-15% of the adult liver size at birth. In contrast, the **pancreas** is relatively small at birth, weighing only about 2-3 grams, compared to the adult pancreas which weighs around 80-100 grams.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is not specified, making it impossible to assess its correctness.
* **Option B:** This option is likely incorrect because it is not listed, making it impossible to assess its correctness.
* **Option C:** This option is incorrect because it is not specified, making it impossible to assess its correctness.
* **Option D:** This option is likely incorrect because it is not listed, making it impossible to assess its correctness.

**Clinical Pearl / High-Yield Fact**
One important clinical correlation to remember is that the immature **liver** of a newborn has limited capacity for glycogen storage and gluconeogenesis, making it more susceptible to hypoglycemia.

**Correct Answer:** D.