contestada

Which set of ordered pairs represents a function?
{( 1,4),( 7.7).( 2.7).( 8. 3)}
{(5. 3), (1.0).(3.3). (1. 1)}
{(7.6).(3.9). ( 8.3). (7,5)}
{(3. 5).(3.1).( 3. 5).( 5.9)}