Correct Answer - B
Form the conservation of the linear momentum.
`mv=(m+2m)v_(CM)`
`implies v+(CM)=v/3`
Let the point whose insantaneous velocity just after collisiion is zero be at a distance `I_(0)` from the centre of mass of the composite system.
`v_(CM)-l_(0)omega=0`
`implies v/3-l_(0)(v/l)=0impliesl_(0)=l/3`
The point is a distance `(2/3)l` from the end where the mass strikes.