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: Microbiology
True about active immunity - 
Select and explain. 
A. Less effective, B. Can be given in immunodeficient state, C. Immunological memory present, D. No lag period
C: Immunological memory present
Answer: C: Immunological memory present 
Explanation: None