The correct answer is option C. "suspicious". When King Arthur and his men returned from battle to Cameliard, the people of Cameliard were suspicious because King Arthur was dressed as peasant. King Arthur did not revealed himself until he defeated the Duke and his companions.
They basically dumped the tea because they refused to pay for any of the taxes. Also they thought that it was unfair that they didn't get a basically fair share on what was happening in their lives.
