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
A malarial survey is conducted in 50 villages having a population of 1 lakh. Out of 20000 slides examined,500 turned out to be malaria positive. The annual parasite incidence is 
Select and explain. 
A. 5, B. 20, C. 0.5, D. 0.4
A: 5
Answer: A: 5 
Explanation: None