**Core Concept**
The described clinical features are indicative of a congenital skeletal disorder characterized by disproportionately short limbs, a large head, and a narrow trunk. This condition is often associated with genetic mutations affecting bone growth and development.

**Why the Correct Answer is Right**
The diagnosis of Achondroplasia, the most common cause of short-limbed dwarfism, can be confirmed through molecular genetic testing. This involves analyzing the FGFR3 gene, which is responsible for encoding a protein that plays a crucial role in endochondral ossification, the process by which cartilage is replaced by bone tissue. Mutations in the FGFR3 gene lead to impaired bone growth, resulting in the characteristic features of Achondroplasia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because X-ray imaging, although helpful in assessing bone structure and development, is not sufficient to confirm the diagnosis of Achondroplasia. While X-rays may show characteristic features such as shortening of the long bones and a large head, they do not provide a definitive molecular diagnosis.

**Option B:** This option is incorrect because ultrasound, although useful in prenatal diagnosis, is not the primary method for confirming the diagnosis of Achondroplasia. Ultrasound can identify some characteristic features, but it does not provide the same level of molecular detail as genetic testing.

**Option C:** This option is incorrect because physical examination, although essential in identifying the clinical features of Achondroplasia, is not sufficient to confirm the diagnosis. Physical examination can only provide a clinical suspicion, which requires further confirmation through molecular genetic testing.

**Option D:** This option is incorrect because blood tests, although useful in assessing the presence of certain biomarkers, are not the primary method for confirming the diagnosis of Achondroplasia. Blood tests can only provide indirect evidence and do not provide the same level of molecular detail as genetic testing.

**Clinical Pearl / High-Yield Fact**
Achondroplasia is the most common cause of short-limbed dwarfism, accounting for approximately 70% of all cases. It is an autosomal dominant disorder, meaning that a single copy of the mutated FGFR3 gene is sufficient to cause the condition.

**Correct Answer:** C. Molecular genetic testing to confirm the diagnosis.