Hxen.com's tips：Every day persisted can learn English well!-->■Learn English Everyday■
acid rain - n. rain that contains dangerous chemicals because of smoke from cars and factories
ozone layer - n. a layer of ozone in the upper atmosphere that prevents dangerous radiation from the Sun from reaching the surface of the Earth
greenhouse gas - n. a layer of gases, such as carbon dioxide, that trap the warmth from the sun in the Earth's atmosphere
executive order - n. an order that comes from the U.S. president or a government agency and must be obeyed like a law
ecosystem - n. a community of organisms and their surroundings that act as a unit
regulator - n. people who oversee enforcement of an official rule or law
emission - n. producing or sending out something, such as energy or gas
authority - n. the power to give orders or make decisions : the power or right to direct or control someone or something
