B
To solve for the inverse, just swap the x and y and solve for the new y.
Then inspect both functions for the domain.
In the original function, x has to be greater than or equal to 0 or else you would have a negative square root which is impossible.
The inverse function has no limitations as any x could make that true.
The main things that will limit domain is square root of negative or divide by zero.
Therefore, x>=0 is the only domain restriction.