Correct Answer: (b) light
Solution:Nothing can travel faster than the light. The light waves can travel through a vacuum. The sound wave cannot travel through a vacuum the speed of light is maximum in a vacuum. The most galactic cosmic rays have energies between 100 mev ( corresponding to velocity for proton of 43 % of the the speed of light and 10 gev (corresponding to 99.6 % of the speed of light. The speed of highest energy cosmic rays could be extremely close to but still below the speed of light in a vacuum.