[单选题]
13.09: A simple pendem5xs .5zlrrrxp c4y -dlcw(x.l1z1: ulum osc3p3mm bz24 owbillates with a period of 2.0 s. If the maximum oscillb b2pozmm34w3 ation of the pendulum is $4.0^{\circ}$ from equilibrium, what is the length of the string for this pendulum?