How does cladistics help us understand phylogeny? A. Cladistics is based on the shared characters between organisms and their network of evolutionary relationships.
B. Cladistics is based on ranking organisms in evolutionary history and predicting prospective future species.
C. Cladistics is based purely on the shared characters between organisms and their ranking in evolutionary history.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

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