**Core Concept**
Subcoracoid dislocation of the shoulder is a type of shoulder dislocation where the humeral head is displaced inferiorly and posteriorly relative to the glenoid cavity. This type of dislocation is often associated with a specific attitude or position of the arm and hand.

**Why the Correct Answer is Right**
The correct answer is related to the mechanism of injury and the position of the arm in subcoracoid dislocation. In this type of dislocation, the arm is typically held in a position of flexion, internal rotation, and adduction. This is because the force of the injury tends to push the humeral head inferiorly and posteriorly, resulting in a position of flexion and internal rotation of the arm.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the typical attitude of the arm in subcoracoid dislocation. While the arm may be in flexion, internal rotation is not typically associated with this type of dislocation.

**Option B:** This option is incorrect because it does not accurately describe the typical attitude of the arm in subcoracoid dislocation. Extension and external rotation are not typically associated with this type of dislocation.

**Option C:** This option is incorrect because it does not accurately describe the typical attitude of the arm in subcoracoid dislocation. While the arm may be in flexion, abduction is not typically associated with this type of dislocation.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the attitude of the arm in subcoracoid dislocation can provide clues to the type of dislocation and the direction of the force of the injury. In this type of dislocation, the arm is typically held in a position of flexion, internal rotation, and adduction.

**Correct Answer: B.**