**Core Concept**
An umbilical hernia in a neonate is a common congenital anomaly where a portion of the abdominal wall is protruded through the umbilicus. This condition can be associated with the presence of an intestinal or omental component, which is a remnant of the omphalomesenteric duct (also known as the vitelline duct).

**Why the Correct Answer is Right**
The omphalomesenteric duct is a normal embryological structure that usually obliterates by the 6th week of gestation. However, remnants of this duct can persist and may become attached to the inner surface of the umbilical hernia. The most common portion of the gastrointestinal tract to be attached is the **caecum**. This is because the caecum is the most proximal part of the large intestine and is in close proximity to the umbilicus during embryological development.

**Why Each Wrong Option is Incorrect**
**Option A:** The small intestine is not typically associated with the omphalomesenteric duct, making it an unlikely attachment in this case.
**Option B:** The stomach is not a common attachment site for the omphalomesenteric duct, and its proximity to the umbilicus is not as significant during embryological development.
**Option C:** The liver and spleen are not directly associated with the omphalomesenteric duct, and their attachments to the umbilical hernia would be unusual.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the presence of an intestinal component within an umbilical hernia can be associated with an increased risk of complications, such as bowel incarceration or obstruction.

**Correct Answer:** C.