If $\vec{F}$ and $\vec{S}$ are force and displacement respectively,and the work done by them is zero,then:

• A
  $\vec{F}$ and $\vec{S}$ are in opposite directions.
• B
  $\vec{F}$ and $\vec{S}$ are in the same direction.
• C
  $\vec{F}$ and $\vec{S}$ are mutually perpendicular.
• D
  $\vec{F}$ is greater than $\vec{S}$.