Questionsare based on the following passage.
If the Dakota Access Pipeline(输油管道) is completed, it will carry nearly half a million bar-rels of oil across four states every day. Energy Transfer Partners (ETP), a Texas-based company behind the $ 3.8 billion project, hopes to finish construction this year. But the Standing Rock Sioux, an American Indian tribe( 部落), is determined to stop the 1,172-mile pipeline from being built. (76)Both sides show no signs of backing down.
The Dakota Access Pipeline was announced in 2014. A section of it will run near the Standing Rock Sioux reservation. A reservation is an area of land set aside for American Indians. The tribe says the construction threatens to destroy historical areas and ancient burial sites. They also say the pipeline could pollute their main water source, the Missouri River. In April, the Standing Rock Sioux began a protest against the project. They camped at the construction site. Since then, thou-sands of people, including people from American Indian tribes, have traveled to the site to join the protest.
ETP says that the pipeline will have built-in safety measures to protect against oil leaks. Work-ers will also monitor it remotely, and will be able to close valves (阀) within three minutes if leaks are detected.
American Indians have been staging a nonviolent protest for months. The protest took a turn last week when police were called to keep the peace between protesters and armed security guards hired by the company.
(77) Twenty-eight people have been arrested since then and charged with interfering with the pipeline construction.
Which of the following is the main idea of the passage?