The 1st and 2nd graph are functions while the 3rd and 4th aren't.
Step-by-step explanation:
The first and second graph doesn't have more than one output for each input. The third and fourth graph isn't a function since there's more than one output for the same input given. If you do the vertical line test, then you'll know which one is a function and which one is not a function. Hope this helps :)
