**Core Concept**
Hemoglobin and Myoglobin are both oxygen-binding proteins that play crucial roles in oxygen transport and storage in the body. They share several structural and functional similarities, reflecting their convergent evolution as oxygen-binding proteins.

**Why the Correct Answer is Right**
Both Hemoglobin and Myoglobin have a heme group, which is a prosthetic group containing iron that binds oxygen. The heme group is bound to a protein globin, which provides structural support and facilitates oxygen binding. This heme-globin complex allows both Hemoglobin and Myoglobin to bind oxygen reversibly, enabling efficient oxygen transport and storage.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while both Hemoglobin and Myoglobin bind oxygen, they have distinct roles in oxygen transport and storage, with Hemoglobin primarily responsible for systemic oxygen transport and Myoglobin storing oxygen in muscle cells.

**Option B:** This option is incorrect because although both proteins contain a heme group, they have different globin chains, with Hemoglobin consisting of alpha and beta chains and Myoglobin consisting of a single polypeptide chain.

**Option C:** This option is incorrect because while both proteins can bind oxygen, their oxygen-binding affinities differ significantly, with Myoglobin having a much higher affinity for oxygen than Hemoglobin.

**Option D:** This option is incorrect because while both proteins are involved in oxygen transport and storage, they have different mechanisms for releasing oxygen, with Hemoglobin releasing oxygen in response to changes in pH and partial pressure of oxygen, whereas Myoglobin releases oxygen in response to increased energy demands.

**Clinical Pearl / High-Yield Fact**
A key difference between Hemoglobin and Myoglobin lies in their oxygen-binding affinities, which reflect their distinct roles in oxygen transport and storage. Understanding these differences is crucial for appreciating the unique physiological and pathological processes involving these proteins.

**Correct Answer: C. Both Hemoglobin and Myoglobin have a heme group that binds oxygen reversibly.**