An object, moving with a speed of $6.25\text{m/s}$, is decelerated at a rate given by:
$$\frac{dv}{dt}=-2.5\sqrt{v}$$
where $v$ is the instantaneous speed. The time taken by the object, to come to rest, would be:

1. A
   $2\text{s}$
2. B
   $4\text{s}$
3. C
   $8\text{s}$
4. D
   $1\text{s}$