**Core Concept**
Hemoglobin A, the most common form of adult hemoglobin, is composed of polypeptide chains that have specific structural and functional roles. The correct composition of hemoglobin A is crucial for its oxygen-binding properties and overall physiological function.

**Why the Correct Answer is Right**
Hemoglobin A is a tetrameric protein consisting of two alpha-globin chains and two beta-globin chains (α2β2). The alpha-globin chains have a molecular weight of approximately 15,000 Da, while the beta-globin chains have a molecular weight of approximately 16,200 Da. The interaction between these chains is essential for the proper folding and function of hemoglobin A, enabling it to bind oxygen in the lungs and release it in the tissues.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately represent the composition of hemoglobin A, which consists of two alpha-globin chains and two beta-globin chains, not two alpha-globin chains and one beta-globin chain.
**Option B:** This option is incorrect because it is missing one of the essential components of hemoglobin A, the alpha-globin chains, which are critical for its structure and function.
**Option C:** This option is incorrect because it contains a mix-up of the globin chains, with two alpha-globin chains and one gamma-globin chain, which is not representative of hemoglobin A.

**Clinical Pearl / High-Yield Fact**
The correct composition of hemoglobin A is essential for its proper function, and alterations in this composition can lead to various hemoglobinopathies, such as sickle cell disease and beta-thalassemia. Understanding the structure and function of hemoglobin A is crucial for diagnosing and managing these disorders.

**Correct Answer:** C. 2 alpha-globin chains and 2 beta-globin chains