1、 He joined the underground to fight against the fascists、他参加了地下组织与法西斯作战。
2、 An underground passage leads to the building across the street、一条地下信道通到街对面的大楼。
3、 Miners work underground、矿工在地下工作。
4、 There is an underground room in the old house、在老房子里有一个地下室。