The theory of punctuated equilibrium is based on the observation that

a. brief periods of intense speciation alternate with long periods of stasis

b. new species appear in the fossil record alongside their unchanged ancestors

c. evolutionary change does not seem to occur at a constant pace

d. all of the above

The appropriate response is all of the above. Punctuated equilibrium is a hypothesis in developmental science which suggests that once species show up in the fossil record they will end up plainly steady, demonstrating minimal transformative change for the greater part of their land history. This state is called stasis.