The force \[F\] on a sphere of radius \['a'\] moving in a medium with velocity \['v'\] is given by \[F=6\pi \eta av\]. The dimensions of \[\eta \] are [CBSE PMT 1997; DPMT 2000]

• A.             \[M{{L}^{-1}}{{T}^{-1}}\]
• B.             \[M{{T}^{-1}}\]
• C.             \[ML{{T}^{-2}}\]
• D.               \[M{{L}^{-3}}\]