**Core Concept**
The axillary artery is divided into three parts based on its anatomical relationships with the pectoralis minor muscle. The second part of the axillary artery is located posterior to the pectoralis minor muscle and is supplied by the posterior circumflex humeral artery. In the event of obstruction, collateral circulation plays a crucial role in maintaining blood supply to the upper limb.

**Why the Correct Answer is Right**
The deep branch of the transverse cervical artery and the subscapular artery form a critical anastomosis with the posterior circumflex humeral artery to maintain blood supply to the upper limb in case of obstruction. This anastomosis occurs in the quadrilateral space, where the subscapular artery contributes to the posterior circumflex humeral artery, ensuring a continuous blood supply to the limb. The deep branch of the transverse cervical artery also contributes to this anastomosis, providing an additional collateral pathway.

**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because it does not involve the posterior circumflex humeral artery, which is the primary artery supplying the second part of the axillary artery.
**Option B:** involves arteries that primarily supply the shoulder joint and surrounding muscles, rather than the second part of the axillary artery.
**Option C:** omits the subscapular artery, which is a critical contributor to the collateral circulation in the quadrilateral space.
**Option D:** involves arteries that primarily supply the scapula and surrounding muscles, rather than the second part of the axillary artery.

**Clinical Pearl / High-Yield Fact**
In cases of axillary artery obstruction, the quadrilateral space anastomosis between the deep branch of the transverse cervical artery and the subscapular artery is crucial for maintaining blood supply to the upper limb. This knowledge is essential for surgeons and radiologists to understand the anatomy of collateral circulation in the upper limb.

**✓ Correct Answer: A. Deep branch of transverse cervical artery & subscapular artery**