Final answer:
Brett grabbing Tor's arm and giving him a warning is the action that initiates a conflict between them, as it demonstrates a significant tension and power struggle. Option number b is correct.
Step-by-step explanation:
The incident in the scene that sets up a conflict between Tor and Brett is when Brett grabs Tor's arm and gives him a warning. This act illustrates a power dynamic and an imposition by Brett on Tor, suggesting an underlying tension and potential for conflict.
The physical act of grabbing and the warning signal a confrontation that goes beyond just words, indicating a more serious disagreement or difference in perspective between the characters.