Answer: part B It gives readers insight into who Casper is and how the group knows him.
part A “What is wrong with you two?” Liam, who was more interested in saving his ice cream than saving the world, asked before they had a chance to explain.
Liam and Tia looked toward the pet store as the four friends dodged into an alleyway, trying not to look too conspicuous. Casper was obviously in disguise himself with his dyed brown hair and beard. The last thing the group needed was for Casper to realize that he had been spotted by his nemesis. The last time he and Trace had met, Trace and his friends had thwarted Casper's plot to create a deadly toxin designed to help him take over the world. That was three months ago, and now it looked like he had somehow escaped from prison and was up to something equally menacing and ominous.