Let $\overrightarrow{a} = \hat{i} - \hat{k}, \; \overrightarrow{b} = x \hat{i} + \hat{j} + (1-x) \hat{k}$ and $\overrightarrow{c} = y \hat{i} +x \hat{j} + (1+x -y) \hat{k}$. Then $[\overrightarrow{a} \overrightarrow{b} \overrightarrow{c}]$ depends on :

Question

( A ) only $x$
( B ) both $x$ and $y$
( C ) only $y$
( D ) neighter $x$ nor $y$