**Core Concept**
Collagen is the most abundant protein in the human body, forming a strong scaffold for connective tissue. Its unique triple-helix structure is stabilized by a specific sequence of amino acids, which is essential for its mechanical strength and function.

**Why the Correct Answer is Right**
The sequence of amino acids in collagen is Gly-X-Y, where X is often proline (Pro) and Y is often hydroxyproline (Hyp). This sequence is crucial for the formation of hydrogen bonds between the amino acids, which stabilizes the triple-helix structure of collagen. The presence of proline and hydroxyproline also helps to restrict the flexibility of the polypeptide chain, allowing collagen to maintain its structure under mechanical stress.

**Why Each Wrong Option is Incorrect**
* **Option A:** This sequence does not match the known Gly-X-Y pattern of collagen.
* **Option B:** This sequence is not specific to collagen and does not reflect its unique amino acid composition.
* **Option C:** This sequence is not a correct representation of the amino acid sequence in collagen.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that collagen's unique sequence of amino acids is a key factor in its ability to provide mechanical strength to connective tissue. This is particularly important in conditions such as osteogenesis imperfecta, where collagen mutations can lead to brittle bones.

**Correct Answer:** D. Gly-X-Y, where X is often proline (Pro) and Y is often hydroxyproline (Hyp).