Final answer:
Darry lets Ponyboy fight in 'The Outsiders because Option(A) "they need all the extra people" for the rumble against the Socs, highlighting the theme of unity within the Greasers.
Step-by-step explanation:
In S.E. Hinton's novel The Outsiders, Darry eventually allows Ponyboy to participate in the rumble because A) They need all of the extra people. Despite Ponyboy's previous injuries and the overall concern for his safety, the Greasers are outnumbered, and every person counts in the upcoming fight against the Socs. Darry realizes that he can't protect Ponyboy from everything and that standing together with the gang is vital for their sense of unity and strength. It's a tough decision, but he consents, acknowledging the importance of not only the physical contribution that Ponyboy would make to the fight but also the moral support his presence provides.