Is it B?
sn2 is max in that (b option) case because in acd
carbication formation is stable sn1 is fav condition
But is not the nucleophile very weak due to the presence of a co-valent bond between N and O in option b?
And in the other cases the nucleophiles are relatively stronger and extent of inversion is proportional to strength of nuclephile..
Yeah but in other cases Sn1 is more favourable so B is the most feasible answer