Which function has an inverse that is also a function?
{(–1, –2), (0, 4), (1, 3), (5, 14), (7, 4)}
{(–1, 2), (0, 4), (1, 5), (5, 4), (7, 2)}
{(–1, 3), (0, 4), (1, 14), (5, 6), (7, 2)}
{(–1, 4), (0, 4), (1, 2), (5, 3), (7, 1)}

If an expression is a function, that means all its x-values in the x,y pairs, are never repeated, the y-values can repeat, but not the x-values

now, an inverse expression of a function, in order to be a function, has to also have unique x-values, x-values that never repeat

however, one characteristic of inverse functions is that, their value pairs, are exactly the same as the original function, but flipped-sideways

namely, if a function has a value pair of   3,5  the inverse will have 5,3
if a function has 7, 11  and 13, 27
the inverse has  11, 7  and 27, 13

so... of all those sets above, if any of those is the value pairs of a function, the x-values must be unique, however, if its inverse expression is also a function, then the y-values must also be unique, namely, if you used the flipped-sideways version, x-values must also be unique

so, will be the one whose x-values AND y-values are unique, let's check