a
As $\mathrm{N} \sin \alpha=\mathrm{mg}$
$\mathrm{N} \cos \alpha=\mathrm{m} \omega^{2} \mathrm{r}$
$\tan \alpha=\frac{g}{\omega^{2} r}$
$\therefore \mathrm{T}^{2} \propto \mathrm{r} \tan \alpha$
$\therefore \mathrm{T}^{2} \propto \mathrm{h} \tan ^{2} \alpha$
for constant $\alpha$
$\mathrm{T}^{2} \propto \mathrm{h}$
Thus when $h$ increases $T$ also increases