Does the relation represent a function?

Question

x 5 10 15
y 8 2 8

-No, because the input value 15 corresponds to two different output values
-No, because there are distinct input values that correspond to the same output value
-Yes, because the input values are distinct
-Yes, because each input value corresponds to exactly one output value
-Yes, because the output values are distinct

Answer 1

since each x is used only once, it's a function