A function maps the independent variable to the dependent variable uniquely, that is, f(x) maps to one and only one value of y, although a particular y value can be mapped by different values of x.
In (1) we have (0,4) and (0,3), zero maps to two different values, so it's not a function.
In (2) we have (7,1) and (7,2), also not a function.
In (3) there are no duplicate values of x to different values of y, so this is a function.
In (4) we have (-2,3) and (-2,5), which is not a function.