Final answer:
Their solution to the puzzle was the principle of reciprocity and the foot-in-the-door technique.
Step-by-step explanation:
Their solution to the puzzle was option C) They attributed it to the principle of reciprocity and the foot-in-the-door technique.
The foot-in-the-door technique is a persuasion strategy where a person is first asked to comply with a small request and then later presented with a larger request. Freedman and Fraser found that participants who agreed to a small request, like putting a small sign in their yard, were more likely to agree to a larger request, such as placing a large sign in their yard. This suggests that people's past behavior can influence their future behavior, and they have a desire to maintain consistency in their actions.