d
Time period $T\, = \,\,2\pi \sqrt {\frac{1}{g}} \,\,\, = \,2\pi {\left( {\frac{1}{g}} \right)^{\frac{1}{2}}}\,\, = 2\pi \frac{{{{({1})}^{\frac{1}{2}}}}}{{{{(g)}^{\frac{1}{2}}}}}$
$\left( {\frac{{\Delta T}}{t}\, \times \,100} \right)\,\% \, = \pm \left[ {\frac{1}{2} \times \frac{{\Delta {l}}}{{l}}\, \times \,100 + \,\frac{1}{{2\,}} \times \,\frac{{\Delta g}}{g}\, \times \,100} \right]$
$ = \pm \left[ {1\,\% \, + \,2\,\% } \right]\,$
$\therefore T\,\, = \pm \,\,3\,\% $