This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
When launching a study, many respondents are invited, some of whom fail to come, this is called 
Select and explain. 
A. Response bias, B. Volunteer bias, C. Selection bias, D. Berkesonian bias
A: Response bias
Answer: A: Response bias 
Explanation: .