**Core Concept**
The question is testing the clinical presentation and complications of **Typhoid Fever**, a systemic infection caused by Salmonella Typhi, which affects the gastrointestinal tract and can lead to multi-organ involvement.

**Why the Correct Answer is Right**
The patient's symptoms, including prolonged fever, abdominal discomfort, splenomegaly, and leucopenia, are consistent with typhoid fever. The development of an acute abdominal event, leading to death, is likely due to **Intestinal Perforation**, a known complication of typhoid fever. Intestinal perforation occurs due to the necrosis of the intestinal wall, which can be caused by the invasion of Salmonella Typhi into the intestinal mucosa.

**Why Each Wrong Option is Incorrect**
* **Option A:** **Appendicitis** is a possible cause of acute abdominal pain, but it does not explain the prolonged fever, splenomegaly, or leucopenia.
* **Option B:** **Pancreatitis** can cause abdominal pain and leukopenia, but it is not typically associated with splenomegaly or a history of prolonged fever.
* **Option C:** **Meckel's diverticulitis** is a possible cause of acute abdominal pain, but it does not explain the systemic symptoms or the development of splenomegaly.

**Clinical Pearl / High-Yield Fact**
In typhoid fever, the Widal test (a serological test that detects antibodies against Salmonella Typhi) may be positive, but it is not always reliable, especially in the early stages of the disease. A more reliable diagnosis can be made through culture of Salmonella Typhi from blood or stool samples.

**Correct Answer:** C. Intestinal perforation.