**Core Concept**
Down syndrome, also known as trisomy 21, is a genetic disorder caused by an extra copy of chromosome 21. This condition is characterized by intellectual disability, delayed speech, and physical growth delays. Infants with Down syndrome often have distinct physical features, such as a flat face, short neck, and protruding tongue.

**Why the Correct Answer is Right**
Infants with Down syndrome typically have a higher risk of congenital heart defects, such as atrioventricular septal defect, ventricular septal defect, and atrial septal defect. This is due to the altered gene expression and increased oxidative stress caused by the extra copy of chromosome 21. The risk of congenital heart defects in Down syndrome is significantly higher than in the general population.

**Why Each Wrong Option is Incorrect**
**Option A:** Not all infants with Down syndrome have a specific type of gastrointestinal anomaly, such as duodenal atresia. While gastrointestinal anomalies are common in Down syndrome, not all infants will have this particular condition.
**Option B:** Some infants with Down syndrome may have a normal thyroid function. However, thyroid dysfunction, particularly hypothyroidism, is more common in individuals with Down syndrome due to the increased risk of thyroid gland abnormalities.
**Option C:** Infants with Down syndrome are more likely to have a specific type of eye anomaly, such as strabismus or refractive errors, rather than a normal eye exam.

**Clinical Pearl / High-Yield Fact**
Infants with Down syndrome have an increased risk of congenital heart defects, which can be detected through prenatal ultrasound and echocardiography. Early diagnosis and management of these heart defects are crucial for improving the quality of life and reducing mortality in infants with Down syndrome.

**Correct Answer: D. All of the above**