Let $X$ and $Y$ be subsets of $R$ which is the set of all real numbers, the function $F : X \to Y$ defined by $F(x) = x^2$ for $x \in X$ is one-one but not onto if $R^+$ is the set of all $+ve$ real numbers, then :

Question

( A ) $X = Y = R$
( B ) $X = R,\; Y = R^+$
( C ) $X = Y = R^+$
( D ) $X = R^+, \; Y = R$