walk through the elephant-free Peruvian Amazon,for example,
is a much more different experience than a walk through a rain
forest in the Republic of Congo,which has smaller,more tightly
packed trees despite similar climate and soil conditions.The re-
searchers suspect that elephants help drive these ecosystem chan-
ges over hundreds of years.
28.What is the result when elephants consume so many plants?
A.Decreasing woods.
B.Extreme climate.
C.Improvement of forest quality.
D.Increasing elephants.
29.How do the researchers make their idea convincing?
A.By debating.
B.By comparing.