Answer:
The function whose inverse is also a function is:
Explanation:
The inverse of a given function f(x) is also a function if the function is one and one.
a)

As we know that the modulus function is not one-one.
Hence, the inverse of this function is not a function.
b)

We know that a odd-degree polynomial is always one-one.
Hence, the inverse of this function is also a function.
c)

The even degree polynomial is not a one-one function.
Hence, it's inverse is not a function.
d)

We know that the graph of this function is not one-one and hence it's inverse is not a function.