**Core Concept**
The question is testing the understanding of the referred pain mechanism, specifically the viscerosomatic convergence in the context of the rectosigmoid junction. The rectosigmoid junction is innervated by the sympathetic nervous system, which sends pain signals to the spinal cord and then to the brain, where it is perceived as pain in the dermatomal distribution of the same spinal nerve root.

**Why the Correct Answer is Right**
When the rectum is inflated with air, it stretches the rectosigmoid junction, leading to activation of the mechanoreceptors in the rectal wall. These mechanoreceptors send signals to the spinal cord via the sympathetic nervous system, which then converge with the somatic afferents from the skin of the right iliac fossa. This convergence of visceral and somatic pain signals in the spinal cord results in referred pain in the right iliac fossa. The dermatomal distribution of the pain is related to the spinal nerve root that innervates the rectosigmoid junction, which is typically T10-L1.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the referred pain mechanism of the rectosigmoid junction. The ileocecal valve is innervated by the enteric nervous system, which does not contribute to the referred pain in the right iliac fossa.
**Option B:** This option is incorrect because the pain from the rectosigmoid junction is referred to the right iliac fossa, not the left. The left iliac fossa is typically associated with pain from the sigmoid colon or the descending colon.
**Option C:** This option is incorrect because the pain from the rectosigmoid junction is not typically referred to the suprapubic region. The suprapubic region is associated with pain from the bladder or the lower urinary tract.

**Clinical Pearl / High-Yield Fact**
The rectosigmoid junction is a common site for referred pain in conditions such as irritable bowel syndrome (IBS) or rectal cancer. The pain is often described as a dull ache or a feeling of fullness in the right iliac fossa.

**Correct Answer: D. Rovsing's sign**