Answer:
C.Restricted domain :
,

Explanation:
We are given that a function is not one - to-one.

Suppose




Hence,

We know that domain of f(x) is converted into range of
and range of f(x) is converted into domain of
.
Substitute x=3 then we get

Domain of

Range of

Domain of f(x)=

Restricted domain :

Hence, restricted domain of f(x) that makes the function one-to-one .