$A$ block of mass $2 \ kg$ is attached to one end of a massless spring whose other end is fixed at a wall. The spring-mass system moves on a frictionless horizontal table. The spring's natural length is $2 \ m$ and the spring constant is $200 \ N/m$. The block is pushed such that the length of the spring becomes $1 \ m$ and then released. At a distance $x \ m \ (x < 2)$ from the wall,the speed of the block will be:

• A
  $10[1-(2-x)]^{3/2} \ m/s$
• B
  $10[1-(2-x)^2]^{1/2} \ m/s$
• C
  $10[1-(2-x)^2] \ m/s$
• D
  $10[1-(2-x)^2]^2 \ m/s$