A small block A of mass 2 kg is attached to a spring of force constant 1200 Nm$$^{-1}$$, and rests on a smooth horizontal surface at x = 0 as shown in figure. A second block B of mass 1 kg slides along the surface towards A at 6 ms$$^{-1}$$ and sticks to it. Assuming that the collision occurs at t = 0, position x (in meter) of block A as a function of time t is expressed as

A

$$x = 0.173\cos 20t$$

B

$$x = 0.1\cos 40t$$

C

$$x = -0.173\sin t$$

D

$$x = -0.1\sin 20t$$