A force of $-F \hat{k}$ acts on O, the origin of the co-ordinate system. The torque about the point $(1, -1)$ is : <br>

Question

( A ) $-F (\hat{i} + \hat{j})$
( B ) $F (\hat{i} - \hat{j})$
( C ) $F (\hat{i} + \hat{j})$
( D ) $-F (\hat{i} - \hat{j})$