C

Step 1: When a ray of light strikes a plane mirror, the angle of incidence is equal to the angle of reflection.
Step 2: Consider the first mirror: The incident angle is \theta_1, and the reflected angle is also \theta_1, such that the ray changes direction by 2\theta_1.
Step 3: For the second mirror, the ray is now incident at an angle of 90 degrees to the first reflection direction, so the total turn is again doubled, giving an additional 180 degrees twist for the second mirror.
Step 4: When it hits the third mirror, a similar situation occurs, with another doubling of the incident angle turn.
Step 5: Adding these changes gives us a total of 180 + 180 = 360 degrees for three mirrors.
Therefore, the angle between the incident ray and the final reflected ray is 0 degrees (indicating they are parallel in a complete circular turn).
Therefore, the correct answer is 360 degrees which commonly simplifies to a full rotation, indicating that the final ray remains parallel to the incident ray.