**Core Concept**
Meckel's diverticulum is a congenital anomaly of the small intestine, resulting from the incomplete closure of the vitelline duct. It is a true diverticulum, containing all layers of the intestinal wall.

**Why the Correct Answer is Right**
Meckel's diverticulum is a true diverticulum because it contains all layers of the intestinal wall, including the mucosa, submucosa, and muscularis. The vitelline duct, which is the embryological precursor to Meckel's diverticulum, connects the yolk sac to the developing intestine. Incomplete closure of this duct leads to the formation of a diverticulum. The most common complication of Meckel's diverticulum is intestinal obstruction, often caused by a Meckel's diverticulum containing ectopic gastric mucosa that secretes acid and leads to ulceration and narrowing of the intestinal lumen.

**Why Each Wrong Option is Incorrect**
* **Option A:** Meckel's diverticulum is often associated with ectopic gastric mucosa, which can lead to complications such as bleeding and intestinal obstruction. This statement is true.
* **Option B:** Meckel's diverticulum typically presents in the distal ileum, which is a true statement. The distal ileum is the most common location for Meckel's diverticulum.
* **Option C:** Meckel's diverticulum can cause complications such as intestinal obstruction, bleeding, and diverticulitis. This statement is true.

**Clinical Pearl / High-Yield Fact**
A classic clinical trap is to confuse Meckel's diverticulum with other types of diverticula, such as congenital or acquired diverticula of the colon. Meckel's diverticulum is a true diverticulum, whereas other types of diverticula are false diverticula, containing only mucosa and submucosa.

**Correct Answer: A.**