Four types of oscillatory systems: a simple pendulum; a physical pendulum; a torsional pendulum and a spring-mass system, each of same time period is taken to the Moon. If time periods are measured on the moon, which system or systems will have it unchanged? 

• A

  only spring-mass system

• B

  spring-mass system and torsional pendulum

• C

  spring-mass system and physical pendulum

• D

  none of these