The distance travelled by a particle is related to time $$t$$ as $$x = 4t^2$$. The velocity of the particle at $$t = 5$$ s is

A

40 m s$$^{-1}$$

B

25 m s$$^{-1}$$

C

20 m s$$^{-1}$$

D

8 m s$$^{-1}$$