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: ENT
All of the following structures can be viewed through a bronchoscope, EXCEPT: 
Select and explain. 
A. Trachea, B. Vocal cords, C. Subcarinal lymph nodes, D. First segmental division of bronchi
C: Subcarinal lymph nodes
Answer: C: Subcarinal lymph nodes 
Explanation: Subcarinal lymph nodes are mediastinal lymph nodes located around the carina on the other side of the tracheal wall and hence not visualized on bronchoscopy. Involvement of subcarinal nodes may be suspected on bronchoscopy by widening and fixity of the carina and/or paralysis of the vocal cords but these nodes cannot be 'directly visualized'.