There is a tricky aspect to remember about sqrt(x)... The function sqrt(x) is only definied for x >=0 and the function returns only one value for a positive or nul x.
That said... This is the trick:
> x^2 = b^2 : x can be either b or -b
> sqrt(Y) = c : y can only be c^2 (no -c^2) >>> y must be positive by definition of sqrt()
So... the answer is (B) not (E)... and actually, this question is just asking x >= 0.