"A bomb," Katherine mulls this over thoughtfully. "That could be... messy." This is, most likely, an understatement.
However, now is definitely the time for climbing, not thinking about how useful something she doesn't fully understand the mechanisms of - didn't you have to be pretty far away from a bomb to be okay? And weren't the zombies most problematic when they were close? Oh, but it would get rid of a lot of them at once, and that was a good idea - ah, she'd let herself think about it anyway. She shakes her head and speeds up her climb, getting closer to the roof.
There better not be any goddamn zombies up there or she will just punch them all in the face.