**Core Concept**
The process of intubation involves a series of steps to safely secure an endotracheal tube in the patient's airway. This requires a coordinated series of movements and checks to ensure proper placement of the tube. The sequence of steps is critical to prevent complications such as esophageal intubation or laryngeal trauma.

**Why the Correct Answer is Right**
The correct sequence begins with **neck extension and flexion (b)**, which helps to align the oral, pharyngeal, and laryngeal axes, making it easier to visualize the vocal cords with the laryngoscope. **Introduction of laryngoscope (d)** is the next step, allowing the clinician to visualize the vocal cords and pass the endotracheal tube. **Check breath sounds with stethoscope (c)** is performed after the tube is in place to confirm proper placement. **Inflation of cuff (a)** is the final step, ensuring a secure seal around the trachea to prevent leaks and aspiration.

**Why Each Wrong Option is Incorrect**
**Option A:** Inflation of cuff is not the first step in intubation, as the cuff must be placed after the tube is in the correct position.
**Option B:** Neck extension and flexion are essential for visualization, but they are not the initial steps in the intubation process.
**Option C:** Check breath sounds with stethoscope is an important verification step, but it is not the correct sequence for the initial steps of intubation.

**Clinical Pearl / High-Yield Fact**
To remember the correct sequence of intubation, use the mnemonic "NEED" - Neck (extension and flexion), Endoscope (introduction of laryngoscope), Evaluate (check breath sounds), and Deflate (inflation of cuff).

**Correct Answer:** D. Introduction of laryngoscope