Which relation represents a function?

The relation which represents a function is:

           { (-2,2) , (0,2) , (7,2) , (11,2) }

Function--

A function is a relation such that each element of first set is mapped to a unique element of the other set.

i.e. no element has two images.

i.e. it is  a ordered pair of the type: (x,y)

such that no x is mapped to more than one y.

A)

{ (0,0) , (2,3) , (2,5) , (6,6) }

It is not a function.

since 2 is mapped to 3 i.e. the ordered pair (2,3)

and 2 is mapped to 5 as well i.e. the ordered pair (2,5) .

B)

{ (3,5) , (8,4) , (10,11) , (10,6) }

It is not a function.

since 10 is mapped to 11 in the ordered pair (10,11).

and 10 is mapped to 6 in the ordered pair (10,6) .

C)

{ (-2,2) , (0,2) , (7,2) , (11,2) }

It is a function.

since no element of the  first set is mapped to more than one element of the other set.

D)

{ (13,2) , (13,3) , (13,4) , (13,5) }

It is not a function.

since 13 is mapped to more than one element of the other set.