Final answer:
The opinion that 'Taxation without representation was a key issue that led to the Revolutionary War' encompasses the colonists' main grievance with the Stamp Act, which taxed them without their representation in Parliament.
Step-by-step explanation:
The statement that reflects an opinion about the causes of the Revolutionary War, which might be held by a group opposing the Stamp Act, is: 'Taxation without representation was a key issue that led to the Revolutionary War'.
This sentiment was fueled by the imposition of the Stamp Act without colonial representation in Parliament, igniting a response from various colonies who saw it as an infringement on their rights as English subjects. A significant aspect of the growing tension was the belief in no taxation without representation, which marked a move away from previous taxes paid to colonial governments or indirectly through prices, towards a direct tax to the Crown.
Additionally, the fact that the Stamp Act tax was imposed with a goal of supplementing revenue for British government expenses further incensed colonists.