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: Anatomy
Which of the following does not drain into the sub 
mental lymph nodes? 
Select and explain. 
A. Upper lip, B. Tip of tongue, C. Floor of mouth, D. Central lower lip
A: Upper lip
Answer: A: Upper lip 
Explanation: None