**Core Concept**
The anterior shoulder dislocation occurs due to the combination of abduction and external rotation forces applied to the shoulder joint, leading to the displacement of the humeral head anteriorly. This type of injury is often associated with a fall onto an outstretched hand or a direct blow to the shoulder.

**Why the Correct Answer is Right**
The mechanism of injury involves a combination of abduction and external rotation forces that lead to the disruption of the shoulder stabilizing structures, including the labrum, capsule, and ligaments. The external rotation force causes the humeral head to migrate anteriorly, while the abduction force prevents the humerus from returning to its normal position. This combination of forces results in the characteristic anterior shoulder dislocation.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because internal rotation forces would actually contribute to a posterior shoulder dislocation, not an anterior dislocation.
* **Option B:** This option is incomplete and does not provide a sufficient combination of forces to cause an anterior shoulder dislocation.
* **Option D:** This option is incorrect because flexion and adduction forces would not contribute to an anterior shoulder dislocation.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the "dead arm" sign is a classic clinical finding in anterior shoulder dislocations, where the affected arm is often held in a position of abduction and external rotation, and the patient may report numbness or paresthesia in the affected limb.

**Correct Answer: C. Abduction and external rotation.**