**Core Concept**
The axillary artery, a continuation of the subclavian artery, is a vital structure in the upper limb that provides blood supply to the shoulder and arm. It is divided into three parts based on its relationship with the pectoralis minor muscle.

**Why the Correct Answer is Right**
The 3rd part of the axillary artery is the terminal part that continues distally as the brachial artery. It is formed by the anastomosis of the anterior and posterior circumflex humeral arteries around the surgical neck of the humerus. This anastomosis provides a collateral circulation to the arm, which is crucial in case of occlusion of any major artery. The 3rd part of the axillary artery also gives off the terminal branches, including the superior and inferior ulnar collateral arteries.

**Why Each Wrong Option is Incorrect**
**Option A:** The 1st part of the axillary artery is located proximal to the pectoralis minor muscle and does not form an anastomosis around the surgical neck of the humerus.

**Option B:** The 2nd part of the axillary artery is located behind the pectoralis minor muscle and is not directly involved in the anastomosis around the surgical neck of the humerus.

**Option D:** The subclavian artery is the origin of the axillary artery, but it does not form an anastomosis around the surgical neck of the humerus.

**Clinical Pearl / High-Yield Fact**
The anastomosis around the surgical neck of the humerus is an important collateral circulation that can help maintain blood flow to the arm in case of occlusion of the axillary or brachial artery. This is a critical concept in understanding the vascular supply of the upper limb and in planning surgical procedures.

**✓ Correct Answer: C. 3rd part of axillary artery**