**Core Concept**
Eggs are a nutrient-rich food that contains a variety of essential vitamins and minerals. They are an excellent source of protein and are often considered a complete food due to their ability to provide all the necessary nutrients for human growth and development.

**Why the Correct Answer is Right**
Eggs are an excellent source of several B vitamins, including vitamin D, vitamin B12, and riboflavin. They also contain vitamins A, E, and K, as well as vitamin C in smaller amounts. However, eggs do not contain vitamin C, which is an essential vitamin that plays a crucial role in immune function, collagen production, and iron absorption.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because eggs do contain vitamin D, which is essential for calcium absorption and bone health.
**Option B:** This option is incorrect because eggs do contain riboflavin, also known as vitamin B2, which is important for energy production and nerve function.
**Option C:** This option is incorrect because eggs do contain vitamin B12, which is essential for the production of red blood cells and the maintenance of the nervous system.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the nutritional content of eggs can vary depending on the breed of chicken, diet, and cooking method. However, eggs are generally a rich source of essential vitamins and minerals, making them a nutritious addition to a balanced diet.

**Correct Answer:** D. Vitamin C.