Pаssаge 1: Alligаtоrs cоme frоm much older forms. The American alligator is the closest thing Americans have to living dinosaurs. Many people fear alligators and would like to see them disappear from the landscape. Despite people’s fears of alligators, the fact is modern alligators are good indicators of the health of our environment. Fortunately for humans, modern alligators are much smaller than their ancestors, which stretched out to thirty-six feet from nose to tail. Modern alligators rarely grow to more than thirteen feet in length. Modern alligators, like humans, are the top hunters in their environment. Because alligators are at the top of their natural food chain, they are good indicators of the health of their habitats. “The alligator is the best monitor for water and surrounding areas. If the alligators in a lake are in trouble, then people need to examine the water and surrounding environments,” according to one scientist. Alligators live for as long as fifty years. Thus, their bodies become a record of what they have eaten and what they have been exposed to in their environment. After five years of studying alligators in the Florida Everglades, scientists have found alligators becoming thinner, less active, and laying fewer eggs than alligators in Georgia, Louisiana, and Arkansas. So far, there are no good explanations for weight differences. However, future studies of water and general environmental quality are under way to explain the differences. Which of the following is the best restatement of the main idea of this passage?