Why do you think species remain in a stage of stasis?

a. a stable ecological niche leads to absence of selection pressure, which in turn causes species to remain unmodified or in stasis.
b. an unstable ecological niche leads to various selection pressures, which in turn causes the species to remain in a stage of stasis.
c. a stable ecological niche leads to various selection pressures, which in turn causes species to remain unmodified or in stasis.