Question: What is the principle behind Einstein\'s theory of special relativity?

Options:

1. The speed of light is constant in all inertial frames of reference.
2. Mass can be converted into energy.
3. Time is absolute and does not change.
4. Gravity is a force that acts at a distance.

Correct Answer: The speed of light is constant in all inertial frames of reference.

Solution:

Einstein\'s theory of special relativity is based on the postulate that the speed of light in a vacuum is constant and is the same for all observers, regardless of their relative motion.