## **Core Concept**
The question tests knowledge of the sensory innervation of the fingers, specifically which nerves provide sensory supply to the index finger. Understanding the dermatomal and peripheral nerve distribution is crucial for performing local anesthesia.

## **Why the Correct Answer is Right**
The correct answer, **D. Digital nerve**, is right because the digital nerves are responsible for the sensory innervation of the fingers. Each finger has two digital nerves (one for the radial side and one for the ulnar side) that provide sensation to the respective sides of the fingers. For a procedure involving the index finger, anesthetizing a branch of the digital nerve would effectively numb the area.

## **Why Each Wrong Option is Incorrect**
* **Option A:** The **Median nerve** is a major nerve of the hand but is not specifically responsible for the sensory innervation of the individual fingers in a way that would allow for targeted anesthesia of just one finger. It does give off the digital nerves but anesthetizing the median nerve itself would affect a larger area.
* **Option B:** The **Ulnar nerve** primarily supplies the little finger and the ulnar half of the ring finger. It is not responsible for the sensory innervation of the index finger.
* **Option C:** The **Radial nerve** primarily supplies the back of the hand and the thumb, not the index finger.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that for procedures on individual fingers, digital nerve blocks are preferred because they provide targeted anesthesia with minimal impact on hand function. The digital nerves are located on either side of the finger, and a properly performed digital nerve block can provide effective anesthesia for minor surgical procedures.

## **Correct Answer:** D. Digital nerve.