**Core Concept**
The question requires knowledge of the anatomy of the upper limb, specifically the muscles that interact with the shoulder and elbow joints. The correct answer involves identifying a muscle that has a dual function, contributing to both flexion/extension of the elbow and movements of the shoulder joint.

**Why the Correct Answer is Right**
The triceps brachii muscle is a two-joint muscle that spans both the elbow and shoulder joints. It has three heads: lateral, medial, and long. The long head originates from the infraglenoid tubercle of the scapula, which is close to the shoulder joint, while the lateral and medial heads originate from the posterior surface of the humerus. The triceps brachii muscle plays a crucial role in extending the elbow joint and stabilizing the shoulder joint during movements like extension and adduction.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, but typically, muscles like the biceps brachii, brachialis, or brachioradialis are considered for similar questions. However, none of these muscles span both the shoulder and elbow joints like the triceps brachii does.

**Option B:** The deltoid muscle is a three-headed muscle that primarily moves the shoulder joint, but it does not cross the elbow joint.

**Option C:** The pectoralis major muscle is a large muscle that primarily moves the shoulder joint, but it does not cross the elbow joint.

**Option D:** The latissimus dorsi muscle is a large muscle of the back that primarily moves the shoulder joint, but it does not cross the elbow joint.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a shoulder or elbow injury, it's essential to consider the muscles that interact with these joints, as injuries to these muscles can lead to functional deficits and pain.

**Correct Answer:** C. Triceps brachii