The correct answer is B. unarmed colonists.
The reason for this is because the Boston massacre was an event where A mob of colonials were rallying. One of the American colonists got into a brawl with a British soldier so he shot several unarmed colonist.
It couldn't have been other British soldiers because British soldiers didn't pointlessly shoot each other.
The event also didn't involve a conflict between the British and the colonial minutemen.
Also, revolutionary politicians wouldn't have been there because they usually laid back from conflict.
