**Core Concept**
Nitrogen is a colorless, odorless gas that makes up a significant portion of the air we breathe. However, during general anesthesia, the lungs are paralyzed, and gas exchange is impaired, leading to the accumulation of nitrogen in body cavities.

**Why the Correct Answer is Right**
Nitrogen is a noble gas that is poorly soluble in blood and has a low diffusion rate. As a result, when anesthesia is induced, the lungs are unable to exchange gases efficiently, leading to an accumulation of nitrogen in body cavities, such as the stomach, intestines, and bladder. This phenomenon is known as "diffusion hypoxia" and can cause symptoms such as nausea, vomiting, and abdominal distension.

**Why Each Wrong Option is Incorrect**
* **Option A:** Oxygen is not typically accumulated in cavities post general anesthesia. In fact, oxygen levels in the body may actually decrease due to impaired gas exchange.
* **Option B:** Carbon dioxide is a waste product that is typically removed from the body through exhalation, not accumulated in cavities.
* **Option C:** Nitrous oxide is a gas used in general anesthesia, but it is not typically accumulated in cavities. Instead, it is metabolized and exhaled.

**Clinical Pearl / High-Yield Fact**
It's essential to note that diffusion hypoxia can occur in patients with pulmonary disease or those who have undergone a prolonged period of anesthesia. This can be mitigated by gradually reducing the concentration of anesthetic gases and using techniques such as controlled ventilation.

**Correct Answer:** C.