Question

Which relation is a function?

Answer 1

the second one, functions cannot have multiple y values for one x value

Answer 2

A function is a relation which associates every element in the domain to a unique element in the codomain.

In option 1,

2 has more than one image, namely 3 and 7.

In option 3,

11 has more than one image, namely 9 and 5.

In option 4,

3 has more than one image, namely 8 and -2.

Hence, the correct option is 2, where every element in the domain has unique image.