Lungs are to human beings ___ the forest is to the earth.
2个回答

这是“A is to B what C is to D”句式,意思是“A 之于 B 就 像 C 之于 D.”此处 leaves 和lungs 为复数形式,句中谓语动词相应地用复数形式.句意为:树叶对于树就像肺对于人一样.