Because she knows that her neighbors might talk if they saw Boo Radley being led across the street by an eight-year-old girl, Scout places her arm in the crook of Boo Radley's elbow, so that it looks like Boo is accompanying her, rather than the other way around. This shows how obvious the gossipy nature of the town is, that it has been picked up on by Scout to the extent that she knows how it might be misconstrued, whether deliberately or accidentally, and shared. The magnitude of this nature is shown because in all the strangeness of Boo Radley being out of the house, Scout is still aware that the small detail of who is leading whom may be remarked upon. This also shows Scout's loyalty to and care for Boo, as she is thinking of him when she acts like this, to protect him from the gossip of the neighborhood as much as she can. The act of her leading him across the road in the dark also shows the reversal in roles: while Boo is afraid, Scout becomes strong to guide him, a situation which differs greatly from their last encounter, during the fire, where Scout was weak and Boo was there to help her.
We’re all humans, so to feel indifference to one another (those that are suffering), is like betraying our own, according to the author. B is the best answer.
