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
If the prevalence of a disease in a population increases,  the predictive value of a positive test - 
Select and explain. 
A. Decreases, B. Increases, C. Remains constant, D. Becomes compromised
B: Increases
Answer: B: Increases 
Explanation: Effect of prevalence on positive predictive value -
As prevalence of disease increases in a population, PPV of screening test increases.
It is easy to understand, if the number of patients increases in a population the probability of a positive test will also increases.
See following examples