As the experiment of the motion of the pendulum is performed. The motion of the pendulum is periodic.
This periodic nature can be represented the sinusoidal functions.
In the given graph, the position of the pendulum is repeated after a regular interval of time which can be represented by the sinusoidal function whose value oscillates.
Thus, the sinusoidal function can best fit the data represented in the figure.
Hence, the second option is the correct answer.