Two simple pendulums, A and B $,$ are each $3\mathrm{.}0$ m long, and the period of pendulum A is $T.$ Pendulum A is twiee as heavy as pendulum $B.$ What is the period of pendulum $B?$

$2$T

T

$\frac{T}{\sqrt[\phantom{2}]{2}}$

$7\sqrt[\phantom{2}]{2}$