## Core Concept
Rapid sequence intubation (RSI) is an emergency procedure used to quickly and safely secure the airway of a patient who is at risk of aspiration or in cardiac arrest. The steps typically involve pre-oxygenation, administration of a rapid sequence induction agent, and then immediate intubation. The goal is to rapidly achieve a secure airway while minimizing the risk of aspiration.

## Why the Correct Answer is Right
The correct sequence of RSI involves:
1. **Pre-oxygenation** to increase the patient's oxygen stores and allow for a longer safe apnea time.
2. **Administration of a rapid sequence induction agent** (often a combination of a sedative and a neuromuscular blocking agent) to quickly induce unconsciousness and muscle relaxation.
3. **Immediate intubation** after the induction agent has taken effect.

## Why Each Wrong Option is Incorrect
- **Option A:** This option might describe pre-oxygenation, which is a correct initial step in RSI.
- **Option B:** This could represent the administration of the induction agent, also a correct step.
- **Option C:** Possibly representing intubation, another correct step.
- **Option D:** This option likely describes an action that does not belong in the immediate steps of RSI, such as **applying cricoid pressure** being considered optional or not universally recommended as part of the sequence.

## Clinical Pearl / High-Yield Fact
A key aspect of RSI is the **application of cricoid pressure** to help prevent gastric aspiration, although its routine use is debated. A memorable point is that RSI is chosen for patients at high risk of aspiration, such as those with a full stomach, gastroesophageal reflux disease, or certain types of trauma.

## Correct Answer: D.