Final answer:
Paul Revere's engraving was effective in convincing colonists to join the patriot cause by portraying the British soldiers as brutal attackers, generating sympathy for the American colonists.
Step-by-step explanation:
Paul Revere's engraving of the 'bloody massacre on king street' was effective in convincing colonists to join the patriot cause because it portrayed the British soldiers as brutal attackers, generating sympathy for the American colonists. By depicting the soldiers firing ruthlessly into a crowd of unarmed, fleeing civilians, the engraving showcased the cruelty of the British soldiers and their disregard for the lives of the colonists. This characterization of the event resonated with colonists who were already resisting British power and confirmed their fears of a tyrannous government.