Coronavirus makes people sick, usually with a mild to moderate upper respiratory tract illness , similar to a common cold. Its symptoms include a runny nose, cough, sore throat, headache and a fever that can last for a couple of days.
【简答题】Do you know why you sleep? You may think it’s because you’re tired. Or perhaps you’ve been told sleep is good for you. Yet no one knows exactly why or how people sleep. Until the early 1950s, most sci...