VOA慢速英语:太空生活使身体的防御处于警戒状态

identical twin – n. either member of a pair of two babies that are produced from a single egg and who look exactly alike

hyperactivated – adj. made more active than is usual or desirable

alien – adj. not familiar or like other things you have known

congestion – n. a condition where a part of the body is blocked with fluid, such as blood or mucus

DNA (deoxyribonucleic acid) – n. a substance that carries genetic information in the cells of plants and animals

alert – n. the state of being ready for something you have been warned about, such as an attack

anticipate – v. to think of something that will or might happen in the future

expose – v. to cause someone to experience something or to be influenced or affected by something

mission – n. a flight by an aircraft or spacecraft to perform a specific task