Read the following two passages and choose the correct answer to each of the questions.
Modern zoos are very different from zoos that were built fifty years ago. At that time, zoos were places where people could go to see animals from parts of the world. The animals lived in cages that were made of concrete with iron bars, cages that were easy to keep clean. Unfortunately for the animals, the cages were small and impossible to hide in. The zoo environment was anything but natural. Although the zookeepers took good care of the animals and fed them well, many of the animals did not thrive; they behaved in strange ways, and they often became ill.
In modern zoos, people can see animals in more natural habitats. The animals are given more freedom in large areas so that they live more as they would in nature. Even the appearance of zoos has changed. Trees and grass grow in the cages, and the streams of water flow through the areas that the animals live in. There are few bars; instead, there is often only a deep ditch, filled with water, which is called a moat. The moat surrounds an area where several species of animals live together as they would naturally. For example, in the San Diego Zoo, the visitors can walk through a huge special cage that is filled with trees, some small animals, and many birds. This particular kind of cage is called an aviary; it is large enough that the birds can live naturally. The birds in the aviary fly around, make nests in the trees, and hunt for food. At the Zoological Park in New York City, because of special night lights, people can observe nocturnal animals that most people have never seen; these animals are active only at night when most zoos are closed. In a zoo like the Arizona-Sonora Desert Museum, people can see animals that live in special environments like the desert. Some other zoos have special places for visitors to watch animals that live underwater like fish. Still, other zoos have special places for animals that live in cold polar surroundings like the great white bear from the Arctic region.
Modern zoos not only display animals for visitors, but they also preserve and save endangered species. Endangered animals such as the American bald eagle and bison are now living and producing offspring in zoos. For this reason, fifty years from now the grandchildren of today’s visitors will still be able to enjoy watching these animals.
The word “thrive” used in the reading is closest in meaning to____________ .