The temperature of a point in space is given by $T=\left(x^{2}+y^{2}-z^{2}\right) .$ A mosquito located at $(1,1,2)$ desires to fly in such a direction that it will get heat as soon as possible. Then unit vector is :
(b) $-\frac{2}{3} \hat{1}-\frac{2}{3} \hat{j}+\frac{1}{3}$
(i) $\frac{2}{3} \hat{i}-\frac{2}{3} \hat{j}-\frac{1}{3}$
(d) none of these