Question

As Han worked on his paper, he allowed himself to nonjudgmentally consider any idea that came into his mind. In doing so, Han was MOST LIKELY engaged in

Answer 1

reflection
Han was likely engaged in reflection. Another good choice to answer this question/complete this scenario could be "brainstorming" but this sort of indicates a more intentional process of gathering as many ideas as possible. Either one gets at the idea that he was open-mindedly allowing ideas to come to his mind and consider them or use them thoughtfully.