In what instances might punctuated equilibrium occur?
a) when the environment is unusually humid
b) when the environment is rapidly changing
eliminate
c) when the environment is generally stable
d) when the environment experiences gradual change overlong periods of time

Punctuated equilibrium occur when the environment is rapidly changing  eliminate.

Option B

Explanation:

Punctuated equilibrium generally occurs when a sudden massive change occurs in the regular stream. The organisms are forced to adapt themselves to the new environment at the earliest and this process is induced to maintain the equilibrium.

This is the reason why you find an abrupt change in the species without undergoing slow morphological changes. Hence no intermediate forms can be found if you would examine the fossils. Hence to conclude when a species under rapid change to evolve itself to suit the environment it is punctuated equilibrium.