Why is the careful observation of the key sentence important in identifying the main idea of a paragraph?

Can someone me answer this english question

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.

What does the line most likely show about the setting of the scene?