Final answer:
Option B, which indicates that the incidence of type-2 diabetes increases with higher central adiposity, is an example of positive correlation, as it shows two variables increasing together.
Step-by-step explanation:
An example of positive correlation is where two variables increase in unison. From the options provided, Option B is an example of positive correlation. It states that the incidence of type-2 diabetes (T2D) increases as central adiposity increases. This means that as one variable goes up, so does the other, which is a hallmark of a positive correlation.
Another clear example of such a correlation would be the relationship between height and weight, where generally, as height increases, weight also tends to increase. It is important to note, however, that positive correlation does not necessarily imply causation; it merely indicates that there is a relationship between the two variables where one increases as the other does.