Question

If the time displacement time graph for a particle is parallel to time axis, what is the velocity of the particle is​

Answer 1

velocity is became zero

Answer 2

If Displacement is parallel to time, that means the displacement is not changing i.e displacement is constant. If displacement is not changing, that means that the object is stationary. Since displacement is constant, on differentiating distance, we get velocity which will be zero. I hope you understand this.