**Core Concept:**
The question is about a pediatric patient presenting with bloody diarrhea, oliguria (abnormally low urine output), and hypertension (abnormally high blood pressure). These symptoms suggest a syndrome known as Hemolytic-Uremic Syndrome (HUS), which is mainly caused by Shiga toxin-producing E. Coli (STEC) infection. STEC is a group of bacteria that can produce Shiga toxins, which are responsible for triggering HUS.

**Why the Correct Answer is Right:**
The correct answer, E. Coli (Escherichia coli), is chosen due to its association with the production of Shiga toxins. Shiga toxins are the primary cause of Hemolytic-Uremic Syndrome (HUS), which presents with the mentioned symptoms. In this specific case, the E. coli is referred to as Shiga toxin-producing E. coli (STEC) to differentiate it from other types of E. coli.

**Why Each Wrong Option is Incorrect:**

A. Salmonella: Salmonella produces Shiga-like toxins, but the specific toxins produced by STEC (Shiga toxin-producing E. coli) cause HUS, not Salmonella.

B. Rotavirus: Rotavirus is a common cause of viral gastroenteritis (inflammation of the intestines), but it is not responsible for HUS.

C. Streptococcus pneumoniae: This is a cause of bacterial pneumonia and meningitis but not associated with HUS.

D. Enteropathogenic E. coli (EPEC): EPEC is another type of E. coli associated with diarrhea but not HUS.

**Clinical Pearl:**

In the context of HUS, it is essential to differentiate between the various types of E. coli causing gastrointestinal illnesses. STEC (Shiga toxin-producing E. coli) is the correct answer as it is the specific type associated with HUS due to its production of Shiga toxins. This knowledge is crucial for appropriate diagnosis and management of pediatric patients presenting with the mentioned symptoms.

**Correct Answer:** D. Enteropathogenic E. coli (EPEC)