In order for a relation (a set of ordered pairs) to be considered a <em>function</em>, every value in the <em>domain</em> (the set of all the first numbers in the pair) is associated with one value in the <em>range</em> (the set of all second numbers in the pair). This is easiest to see visually. Our domain is the set {2, 3, 4, 5} and our range is the set {4, 6, 8, 10}, and we can visualize the ordered pair (2, 4) as an "arrow" starting a 2 in the domain and ending at 4 in the range. When seen this way, a relation is a function if <em>every value in the domain only has one arrow coming out of it</em>. We can see from the attached picture that the ordered pairs in the problem are a function, so this statement is true.