Which relation represents a function

1) {(0,3), (2,4), (0,6)}
2) {(-7,5), (-7,1), (-10,3), (-4,3)}
3) {(2,0), (6,2), (6,-2)}
4) {(-6,5), (-3,2), (1,2), (6,5)}

Thanks in advance.

1. NO! Two pairs have the x-value of 0
2. NO! Two pairs have the x-value of -7
3. NO! Two pairs have the x-value of 6
4. YES! Each pair has a unique x-value.

Simply put: for each x there is a single y, so only 4 meets that parameter.