What is the largest possible domain for the function

Question

f(x) = ~x + ~(4 - x^2) ?
a.{x: O:::;x:::;2,x ER}
b.{x: -2 :::;x :::;2, x E R}
c.{x: 0 s X :s 4, X E:R}
d.{x: x 2': 2, x ER}