书籍 Total English - 中高级 - 第 3 单元 - 第 1 课

used to express that something happens continuously from the beginning to the end of a period of time

scientific knowledge put into practice in a particular area, especially in industry

ready for being used or acquired

可用的,空闲的

a long movie full of adventure that could be about a historical event

occurring or existing before what is being mentioned