A mapping diagram shows a relation, using arrows, between inputs and outputs for the following ordered pairs: (negative 6, 0), (2, 1), (negative 7, negative 4), (11, 2), (3, 2).

What is the domain of the relation?

{x| x = –4 , 0, 1, 2}.
{x| x = –7, –6, 2, 11, 3}.
{y| y = –4, 0, 1, 2}.
{y| y = –7, –6, 2, 11, 3}.