**Core Concept**
The question is testing the understanding of the referred pain pattern associated with cholecystitis, specifically the involvement of the spinal nerve segments that transmit pain from the gallbladder to the shoulder region. This phenomenon is related to the somatic innervation of the gallbladder, which is derived from the phrenic nerve (C3-C5).

**Why the Correct Answer is Right**
The phrenic nerve, a branch of the cervical plexus, provides somatic innervation to the diaphragm and the peritoneum covering the diaphragm. The pain from the inflamed gallbladder is referred to the dermatome of the phrenic nerve, specifically the C3-C5 segments. This is due to the shared innervation of the phrenic nerve with the diaphragm and the peritoneum. As a result, the pain is referred to the shoulder region, particularly the posterior aspect.

**Why Each Wrong Option is Incorrect**
**Option A:** The intercostal nerves (T1-T12) provide somatic innervation to the intercostal muscles and the parietal pleura. While they do contribute to the pain pattern of pleurisy, they are not primarily involved in the referred pain of cholecystitis.

**Option B:** The thoracic nerves (T1-T12) provide somatic innervation to the muscles of the thoracic wall and the parietal pleura. However, they are not directly involved in the referred pain of cholecystitis, which is primarily mediated by the phrenic nerve.

**Option C:** The subcostal nerve (T12) provides somatic innervation to the abdominal muscles and the parietal peritoneum. While it may contribute to the pain pattern of abdominal conditions, it is not primarily involved in the referred pain of cholecystitis.

**Clinical Pearl / High-Yield Fact**
The referred pain of cholecystitis is often described as a "pleuritic" pain, radiating to the shoulder region. This is due to the shared innervation of the phrenic nerve with the diaphragm and the peritoneum.

**Correct Answer: C. C3-C5**