Given a graph of the period versus the mass.
From the graph, the plot of the period versus mass is almost a horizontal line. That is as the mass of the pendulum increases, its period remains constant. The period of the pendulum is unaffected by the change in the mass. Thus the period of the pendulum does not depend on its mass.
This is also consistent with the formula of the period which is,
Where L is the length of the pendulum and g is the acceleration due to gravity.
As seen from the formula the period of the pendulum does not depend on the mass of the pendulum.
Therefore the period of the pendulum does not depend on its mass, this is conclusive from the given data.