**Core Concept**
Schistosomiasis, a parasitic disease caused by Schistosoma haematobium, can lead to bladder calcification due to chronic inflammation and fibrosis. This calcification can take on a distinctive radiographic appearance.

**Why the Correct Answer is Right**
The calcification in schistosomiasis is characterized by the presence of small, sand-like deposits within the bladder wall, often giving the appearance of a "fetal head" or "egg on a string" on radiographs. This is due to the chronic irritation caused by the eggs of the parasite, leading to fibrosis and calcification of the bladder wall. The calcification is typically seen in the upper or lower poles of the bladder and can be associated with other signs of schistosomiasis, such as bladder stones or ureteral strictures.

**Why Each Wrong Option is Incorrect**
**Option A:** Tuberculosis of the bladder typically presents with ulceration and caseation, leading to thickening of the bladder wall, but not calcification resembling a fetal head.

**Option C:** Chronic cystitis may lead to bladder wall thickening and calcification, but the calcification pattern is usually more diffuse and not as distinctive as in schistosomiasis.

**Option D:** Malignancy of the bladder can lead to calcification, but the pattern is typically more irregular and not as characteristic as the "fetal head" appearance seen in schistosomiasis.

**Clinical Pearl / High-Yield Fact**
Schistosomiasis is a classic cause of bladder calcification, and the "fetal head" appearance on radiographs is a distinctive clue to its diagnosis. This pattern should be considered in the differential diagnosis of bladder calcification, especially in patients with a history of travel to endemic areas.

**✓ Correct Answer: B. Schistosomiasis**