$A$ body of mass $0.4 \text{ kg}$ performs simple harmonic motion. It experiences a restoring force of $0.4 \text{ N}$ when its displacement from the mean position is $4 \text{ cm}$. The force constant and magnitude of acceleration respectively are

• A
  $10 \text{ N/m}, 1 \text{ m/s}^2$
• B
  $5 \text{ N/m}, 0.5 \text{ m/s}^2$
• C
  $10 \text{ N/m}, 0.5 \text{ m/s}^2$
• D
  $5 \text{ N/m}, 1 \text{ m/s}^2$