Explanation:
Using the concept of inverse function, it is found that the first graph shows a function whose inverse is also a function.
----------------------------------------
A function f(x) will only have an inverse function if: f(a) = f(b) \leftrightarrow a = bf(a)=f(b)↔a=b , that is, a value of y will have only one respective value of x.
----------------------------------------
In the first graph, for each value of y, there is only one value of x, so the inverse is also a function, and this is the correct option.
In the second graph, for example, y = 0 when x = -1 and when x = 1, so the inverse is not a function.
In the third graph, for example, y = -3 when x = 0 and x = 2, so the inverse is not a function.
In the fourth graph, for example, y = 1 for two values of x, so the inverse is not a function.