Four Pendulums Are Hung from a Light Rod That Is

Multiple Choice

Four pendulums are hung from a light rod that is free to rotate about its long axis. The pendulums have lengths L, 2L, L/2 and L, and masses m, m/2, 2m and 4m respectively. Pendulum 1 is set to swing at its natural frequency. Which of the other three will, over time, also oscillate at the same frequency?

A) (2)
B) (3)
C) (4)
D) (2) and (3)
E) all three