**Core Concept**
Carcinoma of the right colon typically presents with non-specific, early symptoms due to its slow growth rate and late involvement of the bowel wall, which contrasts with left-sided colon cancers that often present with obstructive symptoms.

**Why the Correct Answer is Right**
The right colon, being rich in lymphatic drainage, often metastasizes early in the disease course, leading to occult blood loss and iron deficiency anemia. This, combined with the relatively non-specific nature of the symptoms such as weakness, fatigue, and weight loss, makes it challenging to diagnose right-sided colon cancer in its early stages. The lack of obstructive symptoms such as abdominal pain, vomiting, and constipation is a key distinguishing feature of right-sided colon cancer.

**Why Each Wrong Option is Incorrect**
**Option A:** Abdominal pain is more commonly associated with left-sided colon cancer due to its tendency to cause obstruction.
**Option B:** Diarrhea is not a typical presenting symptom of right-sided colon cancer, which more commonly presents with constipation or altered bowel habits.
**Option C:** Hematochezia (passage of fresh blood per rectum) is more commonly associated with left-sided colon cancer due to its tendency to cause bleeding.

**Clinical Pearl / High-Yield Fact**
A key clinical pearl is that right-sided colon cancer often presents with iron deficiency anemia in the absence of overt bleeding, making it essential to investigate for occult blood loss in patients with unexplained anemia.

**Correct Answer:** B