The equation given, S = vt, represents the distance covered by a moving car in rectilinear motion. In this equation, S represents the distance, v represents the speed of the car, and t represents the time.

Option 1 states that the car undergoes a uniform acceleration. Acceleration refers to the change in velocity over time. In this equation, there is no term representing acceleration, so option 1 is not correct.

Option 2 states that the car undergoes a non-uniform acceleration. Non-uniform acceleration means that the acceleration changes over time. Again, there is no acceleration term in the equation, so option 2 is also not correct.

Option 3 states that the car undergoes a uniform velocity. Velocity refers to the speed and direction of an object. In the given equation, both speed(v) and time(t) are constant terms, meaning there is no change in velocity. Therefore, option 3 is the correct answer.

Option 4 states that the car undergoes a non-uniform velocity. Non-uniform velocity means that the velocity changes over time. However, since there is no acceleration term in the equation, the velocity remains constant, making option 4 incorrect.

In conclusion, the car undergoes a uniform velocity, as