This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Excessive bleeding during hemothorax is caused usually by- 
Select and explain. 
A. Vena cava, B. Internal mammary artery, C. Heart, D. Major artery
D: Major artery
Answer: D: Major artery 
Explanation: Massive Hemothorax:

Collection of more than 1500 ml of blood in the pleural cavity is called massive hemothorax.
Massive hemothorax is usually the result of major pulmonary vascular injuries or major arterial wounds, while minor lung injuries cause small hemothorax.

Also know 

Most common cause of hemothorax is due to injuries of Internal mammary Artery.