The correct option is
D Pioneer
The correct answer is Option D.
We are to select the word that means 'one who leads others in any field'.
On observation of the given options, it can be noticed that all the four options are words for people who hold authority. Thus we should check the meaning of every word to understand the minor difference in their meaning so that we can get the correct answer.
Option A- BOSS means a person in charge of an organization or a workplace.
Option B- CHAIRMAN means a person chosen to preside over a meaning or a person who controls a meeting.
Option C- OFFICER means a person holding authority, especially one with a commission in the armed services.
Option D-PIONEER means one who is the first leader in any field i.e. one who leads in every field.
Thus we can conclude that the desired answer is Option D.