**Core Concept**
The facial nerve (cranial nerve VII) is responsible for motor function of the muscles of facial expression, as well as taste sensation from the anterior two-thirds of the tongue. During nerve conduction studies, the facial nerve is stimulated to assess its integrity.

**Why the Correct Answer is Right**
Facial nerve stimulation during testing of the nerve will result in the contraction of the muscles of facial expression. This is because the facial nerve has a motor component that innervates these muscles. When the facial nerve is stimulated, it activates the motor neurons that control the muscles of facial expression, leading to contraction of these muscles. The orbicularis oculi muscle, which surrounds the eye, is often used to assess facial nerve function.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the facial nerve is not responsible for muscle contraction in the upper limb. The ulnar nerve and median nerve are responsible for motor function in the hand and forearm.
**Option B:** This option is incorrect because the glossopharyngeal nerve (cranial nerve IX) is responsible for taste sensation from the posterior one-third of the tongue, not the anterior two-thirds.
**Option C:** This option is incorrect because the vagus nerve (cranial nerve X) is responsible for parasympathetic innervation of various organs, including the heart and lungs, but not for muscle contraction of the face.

**Clinical Pearl / High-Yield Fact**
The facial nerve is often tested during a physical examination by asking the patient to whistle or show their teeth, which requires contraction of the orbicularis oris and zygomaticus muscles, respectively.

**Correct Answer: C. Facial nerve stimulation during testing of the nerve indicated by contraction of the orbicularis oculi muscle.**