**Core Concept**
The biological value (BV) of a protein refers to its ability to provide all the essential amino acids necessary for human growth and maintenance. It is a measure of the protein's quality, indicating its potential to support growth, repair, and maintenance of body tissues.

**Why the Correct Answer is Right**
The biological value of a protein is determined by its amino acid composition and the body's ability to utilize those amino acids. Whey protein, which is derived from milk, has a high BV due to its rich content of essential amino acids, particularly branched-chain amino acids (BCAAs) such as leucine, isoleucine, and valine. The BV of whey protein is maximized due to its optimal ratio of these essential amino acids, which are crucial for muscle growth and repair.

**Why Each Wrong Option is Incorrect**
**Option A:** Casein protein, while rich in calcium, has a lower BV compared to whey protein due to its slower digestion rate and lower content of BCAAs.
**Option B:** Soy protein, although a complete protein, has a lower BV than whey protein due to its lower content of certain essential amino acids, such as methionine and tryptophan.
**Option C:** Egg protein, while having a high BV, is not the maximum among all protein sources, as whey protein has a higher BV due to its optimal amino acid profile.

**Clinical Pearl / High-Yield Fact**
Whey protein's high BV makes it an ideal choice for individuals seeking to build or maintain muscle mass, particularly after exercise or in cases of muscle wasting.

**Correct Answer:** C. Egg protein's high Biological Value is often cited as the highest among protein sources, but whey protein actually has a higher BV due to its optimal amino acid profile.