An insect crawls up a hemispherical surface very slowly. The coefficient of friction between the insect and the surface is $1/3$. If the line joining the centre of the hemispherical surface to the insect makes an angle $\alpha$ with the vertical, the maximum possible value of $\alpha$ so that the insect does not slip is given by
(1) $\cot \alpha = 3$
(2) $\sec \alpha = 3$
(3) $\operatorname{cosec} \alpha = 3$
(4) $\cos \alpha = 3$