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: Social & Preventive Medicine
Which one of the following is not a special incidence rate - 
Select and explain. 
A. Attack rate, B. Secondary attack rate, C. Hospital admission rate, D. Standardized mortality rate
D: Standardized mortality rate
Answer: D: Standardized mortality rate 
Explanation: Special incidence rates 

Attack rate (case rate)
Secondary attack rate
Hospital admission rate