$A$ thin uniform rod,pivoted at $O$,is rotating in the horizontal plane with constant angular speed $\omega$,as shown in the figure. At time $t = 0$,a small insect of mass $m$ starts from $O$ and moves with constant speed $v$ with respect to the rod towards the other end. It reaches the end of the rod at time $t = T$ and stops. The angular speed of the system remains $\omega$ throughout. The magnitude of the torque $(|\vec{\tau}|)$ on the system about $O$,as a function of time,is best represented by which plot?

• A
  $A$ plot showing a linear increase of torque with time for $t < T$ and zero for $t > T$.

  
• B
  $A$ plot showing a constant torque for $t < T$ and zero for $t > T$.

  
• C
  $A$ plot showing a parabolic increase of torque with time for $t < T$ and zero for $t > T$.

  
• D
  $A$ plot showing a linear decrease of torque with time for $t < T$ and zero for $t > T$.