The period of oscillation of a simple pendulum is $T=2 \pi \sqrt{\frac{L}{g}} .$ Measured value of $L$ is $20.0 \mathrm{~cm}$ known to 1 mm accuracy and time for 100 oscillations of the pendulum is found to be 90 s using a wrist watch of 1s resolution. The accuracy in the determination of $g$ is
(A) $3 \%$
(B) $1 \%$
(C) $5 \%$
(D) $2 \%$