$A$ clock is designed based on the oscillations of a spring-block system suspended vertically in the absence of air resistance. Assume it shows the correct time when a spring of stiffness $k$ and a block of mass $m$ are used. If the block is replaced by another block of mass $4m$,choose the correct option.

• A
  The clock runs slow by $0.5 \text{ s}$ for every one second.
• B
  The clock runs fast by $0.5 \text{ s}$ for every one second.
• C
  The clock runs fast by $1 \text{ s}$ for every one second.
• D
  The clock runs slow by $1 \text{ s}$ for every one second.