Final answer:
In a Venn diagram, elements of contrast appear on the outer edges of the left circle or the right circle, unique to each set. The correct option is D.
Step-by-step explanation:
When using a Venn diagram to compare and contrast two sets, the elements that are unique to each set should appear in the non-overlapping regions of the circles or ovals. This means elements that are unique to the first set should appear in the left circle and elements that are unique to the second set appear in the right circle.
The elements that both sets have in common should be placed in the overlapping region. Therefore, elements of contrast appear on the outer edges of either the left circle or the right circle, but not in the overlapping region. Hence, D is the correct option.