To find a <em>true positive</em>, we need to find the chance of two events happening: <em>an infection is detected and the person has said infection</em>. That means that it is when <em>both I and D are true</em>.
When in a set, two events happen simultaneously, it is shown with a ∩ (intersection) symbol.
That means that a true positive is shown as P (I ∩ D)
So the graph shows a division problem. the green parts represent 1/4 of the rectangle. and that 1/4 has been cut into 5 parts. so i think it would be d.