**Core Concept**
The external branch of the superior laryngeal nerve (EBSLN) plays a crucial role in thyroid surgery due to its close proximity to the surgical field. It is responsible for innervating the cricothyroid muscle, which is essential for pitch regulation during vocalization.

**Why the Correct Answer is Right**
The EBSLN is at a higher risk of injury during thyroid surgery due to its anatomical course, which lies close to the thyroid gland and the recurrent laryngeal nerve. The nerve is often encountered during the dissection of the thyroid gland, particularly during the identification and preservation of the superior pole vessels. The EBSLN is a branch of the superior laryngeal nerve, which arises from the vagus nerve (cranial nerve X). Damage to the EBSLN can lead to impairment of the cricothyroid muscle, resulting in hoarseness or a change in the pitch of the voice.

**Why Each Wrong Option is Incorrect**
**Option A:** Right recurrent laryngeal nerve injuries are less common during thyroid surgery because the nerve is generally located more posteriorly and is not as frequently encountered during the surgical dissection.
**Option B:** Left recurrent laryngeal nerve injuries can occur during thyroid surgery, but they are less common than EBSLN injuries. The left recurrent laryngeal nerve is longer and more tortuous, making it less susceptible to damage.
**Option C:** The internal branch of the superior laryngeal nerve is responsible for sensory innervation to the larynx and is not typically injured during thyroid surgery.

**Clinical Pearl / High-Yield Fact**
The EBSLN is more susceptible to injury during thyroid surgery due to its close proximity to the surgical field. Surgeons should take extra care to identify and preserve this nerve to avoid postoperative voice changes.

✓ Correct Answer: D. External branch of superior laryngeal nerve