This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen & Pelvis, Subject name: Anatomy
Which of the following duct commences in the abdomen as an elongated lymph sac of the cistema chyli is 
Select and explain. 
A. Thoracic duct, B. Gartner's duct, C. Bile duct, D. Hepatic duct
A: Thoracic duct
Answer: A: Thoracic duct 
Explanation: (Thoracic duct) (270 - BDC - 1) (132 - Snell 7th)THORACIC DUCT:- Begins as continuation of the upper end of the cisterna chyli near the lower border of the twelfth thoracic vertebrae and enters the thorax through the aortic opening of the diaphragm, on the right side of the descending aorta* At the roof of the neck, the thoracic duct receives the left jugular, subclavian and bronchomediastinal lymph trunks, although they may drain directly into the adjacent large veins.