**Erb's Palsy Explanation**

**Core Concept**
Erb's palsy is a form of brachial plexus injury, specifically affecting the upper trunk (C5-C6) and sometimes the middle trunk (C7). It occurs due to damage to the nerves that control the muscles of the shoulder and elbow.

**Why the Correct Answer is Right**
Erb's palsy typically results from a birth injury, such as a difficult delivery or shoulder dystocia, which can cause the nerves to stretch or tear. The injury can lead to weakness or paralysis of the muscles of the affected arm, including the deltoid and biceps. The suprascapular nerve, which originates from the upper trunk, is often involved, causing weakness of the supraspinatus and infraspinatus muscles.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Erb's palsy specifically affects the upper trunk (C5-C6) and sometimes the middle trunk (C7), whereas Klumpke's palsy affects the lower trunk (C8-T1).

**Option B:** This option is incorrect because Erb's palsy is not caused by a direct injury to the brachial plexus; rather, it is a stretching or tearing of the nerves during a difficult delivery.

**Option C:** This option is incorrect because obstetric brachial plexus injury is a broader term that encompasses both Erb's palsy and Klumpke's palsy, whereas Erb's palsy specifically refers to the injury of the upper trunk.

**Option D:** This option is incorrect because Erb's palsy typically presents with weakness or paralysis of the muscles of the shoulder and elbow, rather than the wrist and hand.

**Clinical Pearl / High-Yield Fact**
The Erb's palsy mnemonic "Waiter's Tip" can help remember the muscles affected: Wrist (W) - Wrist drop, Arm (A) - Arm weakness, Tip (T) - Triceps weakness, and Inability (I) to extend the elbow.

**Correct Answer: C. Obstetric brachial plexus injury is a broader term that encompasses both Erb's palsy and Klumpke's palsy.**