**Core Concept**
The question is testing the clinical manifestations of a specific worm infestation in a pediatric patient. The condition is characterized by severe anemia, edema, and a characteristic rash, which are all indicative of a systemic parasitic infection.

**Why the Correct Answer is Right**
The described clinical presentation is highly suggestive of hookworm infestation, specifically *Ancylostoma duodenale* or *Necator americanus*. Hookworms cause chronic blood loss in the intestinal lumen, leading to severe anemia, which is evident in this patient with a hemoglobin level of 5 g/dL. The edema is due to hypoalbuminemia, which results from chronic blood loss and impaired protein synthesis. The characteristic rash, known as "ground itch," is caused by the larval migration through the skin. The rash is typically seen in the areas where the larvae penetrated the skin, such as the knees, ankles, and elbows.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because *Trichuris trichiura*, also known as whipworm, primarily causes intestinal symptoms such as diarrhea, abdominal pain, and weight loss, but it is not typically associated with severe anemia or the characteristic rash.
* **Option B:** This option is incorrect because *Ascaris lumbricoides*, also known as roundworm, primarily causes gastrointestinal symptoms such as abdominal pain, nausea, and diarrhea, but it is not typically associated with severe anemia or the characteristic rash.
* **Option D:** This option is incorrect because *Strongyloides stercoralis*, also known as threadworm, primarily causes gastrointestinal symptoms such as diarrhea, abdominal pain, and weight loss, but it is not typically associated with severe anemia or the characteristic rash.

**Clinical Pearl / High-Yield Fact**
In hookworm infestation, the larvae penetrate the skin, causing a characteristic rash, and then migrate to the lungs, where they are coughed up and swallowed, eventually reaching the small intestine, where they mature and cause chronic blood loss.

**Correct Answer:** C.