Answer: D) Set of counting numbers
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Explanation:
Set of whole numbers = {0,1,2,3,4,5,...}
Set of counting numbers = {1,2,3,4,5,...}
The only difference is that 0 is not in the second set. It's not considered a counting number. Other than that, the two sets are pretty much identical. We can see that any counting number is also a whole number, but not vice versa.
The two sets have a common overlap of {1,2,3,4,5,...} which is the set of counting numbers.
If you were to draw a Venn Diagram, it might look like what is shown below. The "counting numbers" circle is completely contained within the "whole numbers" circle. If you randomly pick out something that's a counting number, then it's automatically a whole number. So we consider the set of counting numbers to be a subset of the whole numbers.
