Explanation
Vibration is the periodic motion and the restoring force is the Force due to elastic property of body. Rigid body can not vibrate. Anything has mass and elasticity can vibrate.
Oscillation is also Periodic motion and restoring force is due to weight of the body. even rigid body can oscillate.
IN case of pendulum restoring force is weight of the body itself so the motion is oscillatory motion.
1 metre is the SI unit of length
1 millimetre (mm) is equivalent to $${{10}^{-3}}m$$
1 Angstrom is equivalent to $${{10}^{-10}}m$$
1 Fermi is equivalent to $${{10}^{-15}}m$$
This means fermi is the smallest unit
$$\textbf{Answer}$$
$$\textbf{Hence, the correct option is (c) fermi}$$
Please disable the adBlock and continue. Thank you.