**Core Concept**
Intussusception is a serious medical condition characterized by the telescoping of one segment of the intestine into another, leading to bowel obstruction and potentially life-threatening complications. This condition most commonly affects children but can also occur in adults, often due to a lead point such as a tumor or polyp.

**Why the Correct Answer is Right**
The most common type of intussusception is ileocolic intussusception, where the ileum (the last portion of the small intestine) invaginates into the cecum (the beginning of the large intestine). This type of intussusception is more common in children and is often associated with a lead point such as a lymphoid hyperplasia or a Meckel's diverticulum. The ileocolic intussusception is thought to occur due to the abnormal fixation of the ileum to the cecum, which allows for the telescoping of the intestine.

**Why Each Wrong Option is Incorrect**
**Option B:** Colocolic intussusception is a less common type of intussusception where the colon invaginates into another segment of the colon. While it can occur, it is not the most common type.
**Option C:** Ileocolic intussusception is actually the most common type, not ileoileal intussusception. Ileoileal intussusception is a type of intussusception where the ileum invaginates into another segment of the ileum.

**Clinical Pearl / High-Yield Fact**
In children, the presentation of ileocolic intussusception is often classic, with a triad of abdominal pain, vomiting, and currant jelly stool. This is a critical condition that requires prompt diagnosis and treatment to prevent complications such as bowel necrosis and perforation.

**Correct Answer: C. Ileocolic intussusception**