Choose the word which is different from the rest.

The answer is B. Robber.

A leader is someone who guides or directs a group of people. A chief is the head of a group, organization, or tribe. A boss is a person who is in charge of a group of workers. A robber is someone who steals from another person or group by force or threat of force.

Robber is the only word that is associated with crime. The other words are associated with leadership, authority, or management.