VOA慢速英语:Invasion of Earth Unlikely, Say Researchers

alien – adj. foreign; from a different land or planet

extraterrestrial – adj. coming from our existing outside the Earth

advanced - adj. greatly developed or more modern

pair – n. two people or creatures that do something together

couples – n. two people or creatures belong together

teeth – n. bony structures used for biting or chewing

decay – v. to slowly be destroyed by natural processes

gum – n. tissue surrounding teeth inside the mouth

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