Correct option is B
The correct word for the given blank is ‘undertaken’.
(a)annexed: add (territory) to one's own territory by appropriation.
(b)undertaken: commit oneself to and begin (an enterprise or responsibility); take on.
(c)vanished: disappear suddenly and completely.
(d)jostled: push, elbow, or bump against (someone) roughly, typically in a crowd.
(e)disdained: the feeling that someone or something is unworthy of one's consideration or respect.