If \( \vec{r} \) is the position vector of a particle at time \( t, r^{\prime} \) is the positio...

If \( \vec{r} \) is the position vector of a particle at time \( t, r^{\prime} \) is the position vector of the particle at time \( t^{\prime} \), and \( \overrightarrow{\Delta \mathrm{r}} \) is the displacement vector, then instantaneous velocity is given by
(a) \( \mathrm{V}=\lim _{\Delta \mathrm{t} \rightarrow 0} \frac{\Delta \mathrm{r}^{\prime}}{\Delta \mathrm{t}} \)
(b) \( \mathrm{V}=\lim _{\Delta \mathrm{t} \rightarrow 0} \frac{\Delta \mathrm{r}}{\Delta \mathrm{t}} \)
(c) \( \mathrm{V}=\lim _{\Delta \mathrm{t} \rightarrow 0} \frac{\Delta \mathrm{r}^{\prime}-\Delta \mathrm{r}}{\Delta \mathrm{t}} \)
(d) \( V=\frac{\Delta r}{\Delta t} \)