Based on the context of this excerpt from w. w. jacobs's "the monkey's paw," what does the word placidly mean?

without, the night was cold and wet, but in the small parlour of laburnam villa the blinds were drawn and the fire burned brightly. father and son were at chess, the former, who possessed ideas about the game involving radical changes, putting his king into such sharp and unnecessary perils that it even provoked comment from the white-haired old lady knitting placidly by the fire.

a completing a task in a frantic manner
b having a particular motive for an action
c appearing to be calm and relaxed
d acting harshly or stubbornly