Armadillos aren't the only creatures who rely on gravity to get the ball rolling.犰狳是唯一依靠重力形成球形铁甲团滚动的动物.Cats are creatures of habit — they seem to appreciate a settled routine...猫是一种有固定习性的动物，它们似乎喜欢过一种有规律的生活。creatures...
大脑需要持续供氧。The brain requires a constant supply of oxygen.氧气泡a bubble of oxygen医院中抗甲氧西林金黄色葡萄球菌感染病例不断增长的发生率rising rates of MRSA infections in hospitals...