**Core Concept**
The Anatomical Snuff Box (ASB) is a triangular deepening on the radial, dorsal aspect of the hand at the level of the carpal bones. It is formed by the tendons of the thumb muscles and serves as an important landmark for clinical examination and anatomy.

**Why the Correct Answer is Right**
The muscular boundaries of the Anatomical Snuff Box are formed by the Abductor Pollicis Longus (APL) and Extensor Pollicis Brevis (EPB) tendons on the radial side, and the Extensor Pollicis Longus (EPL) tendon on the ulnar side. These tendons are innervated by the posterior interosseous nerve, a branch of the radial nerve. The APL and EPB muscles are responsible for thumb abduction and extension, respectively.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not a muscular boundary of the Anatomical Snuff Box.
**Option B:** This option is incorrect because it is not a muscular boundary of the Anatomical Snuff Box.
**Option D:** This option is incorrect because it is not a muscular boundary of the Anatomical Snuff Box.

**Clinical Pearl / High-Yield Fact**
The Anatomical Snuff Box is a key landmark for diagnosing radial artery occlusion and De Quervain's tenosynovitis. The tendons of the thumb muscles should be gently palpated to assess for tenderness and swelling, which may indicate underlying pathology.

**Correct Answer: A.**