**Core Concept**
The question is testing the student's knowledge of foodborne illnesses, specifically the incubation period of common pathogens. **Food poisoning** can be caused by various bacteria, viruses, and toxins, each with a distinct incubation period.

**Why the Correct Answer is Right**
Since the boy started vomiting within 3 hours of consumption, the likely causative organism is **Staphylococcus aureus**, which produces a toxin that can cause rapid onset of symptoms. This toxin is pre-formed in the food and can act quickly after ingestion.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the incubation period is too long for the symptoms to appear within 3 hours.
**Option B:** Incorrect as it typically causes symptoms after a longer incubation period.
**Option C:** Incorrect because the symptoms would not appear so quickly.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **Staphylococcus aureus** food poisoning has a short incubation period, typically less than 6 hours, making it a prime suspect in cases of rapid onset vomiting after food consumption.

**Correct Answer:** D. Staphylococcus aureus