**Core Concept**
Beta thalassemia is a genetic disorder affecting the production of the beta-globin chains of hemoglobin. It is characterized by reduced or absent production of beta-globin chains, leading to variable degrees of anemia and other complications.

**Why the Correct Answer is Right**
The correct answer involves molecular genetic analysis, specifically PCR (Polymerase Chain Reaction) and DNA sequencing to identify mutations in the HBB gene encoding the beta-globin chain. This approach allows for the detection of specific mutations associated with beta thalassemia, such as point mutations, deletions, or insertions.

**Why Each Wrong Option is Incorrect**
**Option A:** Hemoglobin electrophoresis is a diagnostic tool used in beta thalassemia but is not the primary method for establishing a diagnosis. It can identify abnormal hemoglobin variants but may not detect all mutations causing beta thalassemia.
**Option B:** Complete blood count (CBC) and blood film examination are helpful in identifying anemia and other hematologic abnormalities in beta thalassemia but are not specific for the diagnosis.
**Option C:** Bone marrow examination is not a primary diagnostic tool for beta thalassemia, although it may be performed to rule out other causes of anemia or to assess bone marrow function.

**Clinical Pearl / High-Yield Fact**
Beta thalassemia is a genetic disorder with a high prevalence in regions such as the Mediterranean, Middle East, and Southeast Asia. Genetic counseling and prenatal testing are essential for families with a history of beta thalassemia.

**Correct Answer: C. Bone marrow examination is not a primary diagnostic tool for beta thalassemia, although it may be performed to rule out other causes of anemia or to assess bone marrow function.**