The dialogue that best helps develop both Sadie and Marco's characters is:
“We’re going to have so much fun,” Sadie said. “I bet we’ll get to meet the band. I bet we’ll even get to hang out with them!”
“We probably won’t even get to go,” Marco said. “I bet the whole show will get canceled and we’ll have a terrible day.”
This exchange effectively showcases Sadie's optimistic nature as she excitedly imagines the possibilities of the event, while Marco's skeptical response highlights his tendency to focus on the negative outcomes. Together, they illustrate the contrast between Sadie's positivity and Marco's brooding skepticism.