A、When the species doesn’t match with its surroundings. B、When the species is threatened by humans. C、When the species shows a t

Scientists have known for years that human life on earth depends on the continued survival of many different kinds of plants, animals and other organisms. This is why governments make laws to protect the environment. In the United States, a major environmental law is the Endangered Species Act of 1973.(23)Earlier laws provided only limited ways to protect native animals considered in danger. The law expanded America’s list of threatened animal species to include foreign animals. It defined the words "endangered" and "threatened." The law extended protection to plants and other organisms. It also required federal agencies to carry out programs to help guarantee the survival of endangered and threatened species. Federal agencies were also barred from taking any step that would harm a listed species or destroy or change its living area. The United States Fish and Wildlife Service calls the Endangered Species Act one of the most far-reaching wildlife conservation laws ever approved.(24)Its purpose is to protect endangered and threatened species and their environments. It also requires the government to take action to help such species.(25)To get this protection, a plant or animal species must be added to the Federal list of wildlife and plants said to be in the greatest need of help. Each species is listed as either endangered or threatened. A species is added to the list when scientists have confirmed that its survival is threatened. The threats may include the destruction of its environment, disease and too much hunting or fishing. Officials say they want to increase the population of the listed species to a level where federal protection is no longer required.
23. What did the environmental laws before 1973 protect?
24. What can we learn from the Endangered Species Act of 1973?
25. When can a plant or animal species get help?