The theory of non-accelerated frame of reference is called

Explanation

The correct answer is the Special theory of relativity. This theory specifically addresses non-accelerated, or inertial, frames of reference and the consistent speed of light in all such frames. It revolutionized the understanding of time and space, formulating how they relate to each other for objects moving at constant velocities. The other options are incorrect because:String theory is unrelated to frames of reference, focusing instead on fundamental particles and forces.General theory of relativity deals with gravity and accelerated frames, extending beyond the scope of the question.Galilean transformation theory is a classical framework that does not incorporate relativistic effects, which are crucial for understanding non-accelerated frames in the context of modern physics.