Question 1122434
Note: when an expression is under the square root, if the result need to be a real number it need to be greater than or equal to zero. If it doesn't need to be(can be complex technically), there's no restrictions.
When y and x are defined in all real numbers:
A: {{{x+6>=6}}}
   {{{x>=6}}}
B: {{{2-x>=0}}}
   {{{x<=2}}}
C,D: none because any real number x gets a real outcome y.


When they're defined in complex set:
No restrictions at all. Any value gets a complex result.