14. $f ( x ) = \left\{ \begin{array} { l } x , \quad \text { if } x \text { is rational } \\ 0 , \quad \text { if } x \text { is irrational } \end{array} \right.$ and
$$g ( x ) = \left\{ \begin{array} { l }
0 , \quad \text { if } x \text { is rational } \\
x , \quad \text { if } x \text { is irrational. }
\end{array} \text { Then } \mathrm { f } - \mathrm { g } \right. \text { is: }$$
(a) one-one and into\\
(b) neither one-one nor onto\\
(c) many one and onto\\
(d) one-one and onto\\