How many are functions?

1.(5,2)(9,0)(2,5)(5,7)
2.(-2,5)(-4,7)(-9,10)(-11,12)
3.(3,-5)(7,9)(2,3)(-5,9)
4.(4,7)(-2,5)(-2,6)(-5,10)
10 POINTS PLS HELP!