**Core Concept**
Post-operative ileus (POI) is a temporary cessation of normal bowel function following surgery, characterized by a delay in the passage of gas and stool. The recovery of bowel function in POI is a complex process involving the coordinated action of the enteric nervous system, gut hormones, and the restoration of gastrointestinal motility.

**Why the Correct Answer is Right**
The small intestine is the first part of the gastrointestinal tract to recover from post-operative ileus due to its rich blood supply and relatively low metabolic demand. The enteric nervous system, which regulates gut motility, is also more active in the small intestine compared to the large intestine. As a result, the small intestine is able to recover from the effects of surgery and anesthesia, allowing for the resumption of normal bowel function. This process is facilitated by the release of gut hormones such as gastrin and cholecystokinin, which stimulate the contraction of intestinal smooth muscle.

**Why Each Wrong Option is Incorrect**
**Option A:** The colon is not the first to recover from post-operative ileus due to its higher metabolic demand and lower blood supply compared to the small intestine.
**Option B:** The stomach is not the first to recover from post-operative ileus due to its lower blood supply and higher metabolic demand compared to the small intestine.
**Option C:** The rectum is not the first to recover from post-operative ileus due to its lower blood supply and higher metabolic demand compared to the small intestine.

**Clinical Pearl / High-Yield Fact**
The recovery of bowel function in post-operative ileus can be accelerated by the use of prosthetic agents such as metoclopramide and erythromycin, which stimulate the contraction of intestinal smooth muscle and enhance gut motility.

**Correct Answer:** A. Small intestine.