This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Surfaces and Grooves, Subject name: Anatomy
A 33-year-old male is admitted to the hospital after a violent, multiple car collision. His blood pressure is 89/39 mm Hg, and a central venous line is ordered to be placed. Which of the following structures is used as a landmark to place the tip of the catheter of the central venous line? 
Select and explain. 
A. Carina, B. Subclan aery, C. Superior vena cava, D. Right atrium
A: Carina
Answer: A: Carina 
Explanation: The carina can easily be seen in radiograph. The carina is at the level of T4-5 (plane associated with the sternal angle of Louis). This landmark is commonly used to guide the placement of a central venous line.