The main focus of charles darwin's studies was on the gradual process of adaptation within populations. in other words, microevolution occurs by means of natural selection. although critical to evolution this form of change,

Cannot account by itself for the increase in species diversity over time

i think the answer is b.

hope it

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms