**Core Concept**
Rectal prolapse in a child, accompanied by stunting and growth retardation, suggests a chronic condition that has led to intestinal malabsorption and subsequent nutritional deficiencies. This clinical presentation is often associated with chronic parasitic infections that affect the gastrointestinal tract.

**Why the Correct Answer is Right**
The correct answer is linked to the chronic infection of **Hookworm (Ancylostoma duodenale)**. Hookworm infection causes intestinal blood loss, leading to chronic iron deficiency anemia, which in turn results in growth retardation and stunting in children. The parasite attaches to the intestinal mucosa, causing intestinal malabsorption and subsequent nutritional deficiencies.

**Why Each Wrong Option is Incorrect**
* **Option A:** Ascaris lumbricoides infection primarily causes respiratory and gastrointestinal symptoms, but it is not typically associated with growth retardation and rectal prolapse.
* **Option B:** Giardiasis can cause malabsorption and gastrointestinal symptoms, but it is not commonly linked to rectal prolapse or growth retardation.
* **Option D:** Trichuris trichiura (whipworm) infection can cause rectal prolapse, but it is not typically associated with growth retardation and stunting.

**Clinical Pearl / High-Yield Fact**
Hookworm infection is a major cause of iron deficiency anemia worldwide, particularly in children and pregnant women.

**Correct Answer: C. Hookworm (Ancylostoma duodenale)**