Which of the following statements is false?
a. stock characters are often stereotypes
b. archetypes can be good or bad
c. every story has a protagonist
d. archetypes play supporting roles and are not central characters

The statement "Archetypes can be good or bad" (b) is the statement that is false amongst the options above.
Archetypes are examples or models. Objects, behaviours and other things are patterned on them. An archetype is an example of model behaviour, a good person, an artifact that helps good triumph over evil etc.  In literature, we find situation archetypes, setting archetypes, symbolic archetypes and character archetypes. In short, a model or pattern for every construct needed to write a story or poem etc.