Answer:
The correct answer is - formal operational.
Step-by-step explanation:
According to the Piaget's theory of cognitive development Sean is showing formal operational stage which is characterized by the creating and changing the hypothesis and ideas in their brains and test them without any prior knowledge or evidence.
In this case Sean made his mind to participate in riots to show is frustration without knowing the cause of altercation with a police officer, so it is the cognitive development's formal operational stage.
Thus, the correct answer is - formal operational.