How did Turtle figure out Sam Westings fourth identity in The Westing Game, chapter 27?

Which sentence features a correctly identified compound pronoun in a prepositional phrase? a)she and i will be at the park on tuesday, waiting for mariah and them. b)the gift grandmother brought was for me and him. c)everyone is so sure that he'll be late after traveling with peter and maria. d)after they visit the grand canyon, tianna and mom are going to a spa.