Which of the following relation is a function? a) $(2,4),(3,2),(4,2),(5,2)$ b) $(2,4),(2,5),(2,6),(2,7)$

Step 1 ：Check if each input (x-value) has exactly one output (y-value) for both relations

Step 2 ：Relation a: \( (2,4),(3,2),(4,2),(5,2) \) - Each input has one output

Step 3 ：Relation b: \( (2,4),(2,5),(2,6),(2,7) \) - Input 2 has multiple outputs

Step 4 ：\boxed{\text{Relation a is a function}}