Final answer:
The correct answer is b. Blood exits the armpits through the axillary veins, which subsequently become the subclavian veins deeper in the thorax.
Step-by-step explanation:
Blood leaves the armpits through axillary veins. The axillary vein is the major vein in the axillary region which drains the upper limb and as it passes through the body wall and enters the thorax, it becomes the subclavian vein. The subscapular vein, along with other veins such as the cephalic vein, drains into the axillary vein.
While the subscapular vein focuses on blood from the subscapular region, the cephalic vein starts in the antebrachium and drains blood from the superficial surface of the arm, eventually feeding into the axillary vein as well. The subclavian vein is located deep within the thoracic cavity and receives blood that has been drained by the axillary vein as well as smaller local veins near the scapular region. Therefore, Axillary is the direct answer to this question.