「袋、ご利用ですか」「あ、___です」
Q. What does 大丈夫です most likely mean in this convenience-store exchange?
Translation
"Would you like a bag?" "Oh, I'm fine (no thanks)."
Explanation
In modern usage 大丈夫です frequently functions as a soft refusal: 'I'm fine without it'. Context (being offered a bag) rules out the health reading.