What word requires a spelling change before adding the suffix-er? fast? merry? smart? buy?

How are the characters of tablin and keyn revealed in this excerpt from "the guard" by simon dunbar? a. indirectly through dialogue and by thoughts and actions b. directly through a narrative description c. indirectly through dialogue "where's my horse? " keyn asked. tablin looked around the dirt courtyard. he tried to peer through the shadowy arches of the flowing barrel. he even twisted in his saddle to look across the merchant's bazaar, past tents and warehouses filled with goods. "i don't know," he said. "did you leave it in your mouth? it's the only place i can think of that's big enough." keyn laughed; something got stuck in his throat half way, and he coughed for breath. "i can see you're good to go,” tablin observed as keyn struggled to clear his throat. “go get your horse yourself before i take the job and leave you to rot in the flowing barrel."