**Core Concept**
The underlying principle in this question is the association between certain congenital anomalies and reproductive issues. Dextrocardia is a condition where the heart is positioned on the right side of the chest, which is a characteristic feature of Kartagener syndrome, a primary ciliary dyskinesia.

**Why the Correct Answer is Right**
Kartagener syndrome is an autosomal recessive disorder caused by mutations in the DNAI1 or DNAH5 genes, leading to impaired function of cilia in the respiratory tract, male infertility due to immotile sperm, and situs inversus (a condition where the internal organs are reversed). The husband's chronic sinusitis and lower respiratory tract infections, along with dextrocardia, are indicative of Kartagener syndrome. The presence of immotile sperm is a direct consequence of the underlying ciliary dysfunction.

**Why Each Wrong Option is Incorrect**
**Option A:** Azoospermia refers to the absence of sperm in the ejaculate, which is not directly related to dextrocardia or Kartagener syndrome.

**Option B:** Germinal cell aplasia is a condition characterized by the absence or severe reduction of germ cells in the testes, which is not associated with dextrocardia or Kartagener syndrome.

**Option D:** Isolated gonadotropin deficiency is a condition characterized by low levels of gonadotropins (LH and FSH) leading to hypogonadism, which is not directly related to dextrocardia or Kartagener syndrome.

**Clinical Pearl / High-Yield Fact**
Kartagener syndrome is an important consideration in patients with chronic respiratory infections and infertility, as it highlights the importance of a thorough evaluation of patients with suspected primary ciliary dyskinesia.

**✓ Correct Answer: C. Immotile sperm**