**Core Concept**
Proper laryngoscopy and intubation technique requires careful manipulation of the laryngoscope to visualize the vocal cords, while avoiding unnecessary pressure on surrounding structures.

**Why the Correct Answer is Right**
Levering the laryngoscope on the upper incisor is incorrect because it risks damaging the teeth, particularly the incisors, and may also cause the laryngoscope to slip and lose its optimal position. Instead, the laryngoscope should be used to gently displace the tongue and epiglottis to visualize the vocal cords. The correct technique involves introducing the laryngoscope into the vallecula, a small space between the base of the tongue and the epiglottis, to facilitate direct visualization of the glottis.

**Why Each Wrong Option is Incorrect**
**Option A:** A slight pressure may be applied at the cricoid cartilage, as the cricoid ring is a natural fulcrum point that can be used to facilitate laryngoscope movement and improve visualization of the vocal cords.
**Option B:** The laryngoscope is typically held in the left hand, introduced from the left side of the patient, to allow for optimal visualization of the vocal cords and to avoid obstruction by the right arm.
**Option C:** The neck is indeed flexed with extension at the atlanto-occipital joint, which helps to align the oral, pharyngeal, and laryngeal axes and facilitate direct visualization of the glottis.

**Clinical Pearl / High-Yield Fact**
To avoid complications during laryngoscopy and intubation, it's essential to maintain a secure airway, use proper laryngoscope technique, and ensure adequate muscle relaxation and anesthesia.

**✓ Correct Answer: D. After inseion of laryngoscope, it is levered on the upper incisor to pull up the tongue and visualize the vocal cords**

✓ Correct Answer: D. After inseion of laryngoscope, it is levered on the upper incisor to pull up the tongue and visualize the vocal cords