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
The most definite clinical sign indicating odontogenic infection in to the masticatory space is: 
Select and explain. 
A. Trismus, B. Xerostomia, C. Difficulty in swallowing, D. Swelling in submental area
A: Trismus
Answer: A: Trismus 
Explanation: None