Final answer:
The parts of a Venn diagram are called regions or overlaps.
Step-by-step explanation:
A Venn diagram consists of a box representing the sample space, along with circles or ovals that represent events. The parts of a Venn diagram are called regions. These regions show the different combinations of events and their intersections. The interactions between the circles or ovals in a Venn diagram are called overlaps. So, the correct answer is D) Overlaps.