**Core Concept**
The "red current jelly" appearance of stool in an infant is a characteristic clinical sign of a specific gastrointestinal condition. This sign is associated with a particular pathophysiological process that affects the normal passage of stool through the intestines.

**Why the Correct Answer is Right**
The "red current jelly" appearance of stool in an infant is typically seen in cases of intussusception, a condition where a portion of the intestine has telescoped into another section, causing bowel obstruction and ischemia. The characteristic appearance is due to the presence of blood and mucous in the stool, which gives it a jelly-like consistency and a reddish color. The blood and mucous are a result of the ischemia and edema caused by the intussusception, leading to the shedding of the intestinal mucosa and the release of blood and mucus into the lumen.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the characteristic appearance of stool in intussusception. In fact, the stool in intussusception is typically described as "red current jelly" rather than "currant jelly."

**Option B:** This option is incorrect because it describes a different condition altogether. Meconium ileus is a condition where there is an obstruction of the small intestine due to a blockage of the intestinal lumen by meconium, but it does not typically present with the "red current jelly" appearance of stool.

**Option C:** This option is incorrect because it describes a condition that is not typically associated with the "red current jelly" appearance of stool. Gastroenteritis is a condition that can cause changes in stool consistency and appearance, but it does not typically cause the specific "red current jelly" appearance seen in intussusception.

**Option D:** This option is incorrect because it does not accurately describe the characteristic appearance of stool in intussusception. In fact, the stool in intussusception is typically described as "red current jelly" rather than "coffee ground."

**Clinical Pearl / High-Yield Fact**
The "red current jelly" appearance of stool in an infant is a classic clinical sign of intussusception, and it is essential to recognize this sign in order to diagnose and treat this condition promptly. Intussusception is a medical emergency that requires prompt surgical intervention to prevent bowel perforation and peritonitis.

**Correct Answer: C. Gastroenteritis**