During my final semester of undergrad, I made two signs that read, “Feeling stressed about exams? Have a free hug!” Then I recruited a friend and we stood in the entrance of the campus library, held up the signs, and waited. Passerbys had one of two reactions: Either they quickly looked down at their phones and awkwardly shuffled by, or their faces lit up as they embraced us. Most people were enthusiastic. Some exclaimed, “You made my day!” or “Thank you. I needed this.” One leapt into my arms, nearly toppling me over. After two hours of warm interactions, my friend and I couldn’t believe how energized and happy we felt. The first paragraph serves mainly to

A provide background information necessary to understand the scientific study.

B. introduce the scientific study through a personal anecdote.

C show that not all scientific experiments need to be conducted in a laboratory

D. describe the author's experience as a subject of the scientific study