A uniform disc of mass `M` and radius `R` is mounted on an axle supported in frictionless bearings. A light cord is wrapped around the rim of the disc and a steady downward pull `T` is exerted on the cord. The angular acceleration of the disc is
A. `(T)/(MR)`
B. `(MR)/(T)`
C. `(2T)/(MR)`
D. `(MR)/(2 T)`