Final answer:
Pillownauts willingly choose to participate despite potential challenges.
Step-by-step explanation:
The surprising aspect of "pillownauts" choosing to participate in research studies is option d) Pillownauts willingly choose to participate despite potential challenges. This is surprising because participating in research studies often involves inconveniences, physical discomfort, and even potential risks.
However, some individuals willingly choose to participate in order to contribute to scientific advancements and help improve the lives of others.