And in the last 50 years, 21 million wells have been dug. 过去五十年内 挖了两千一百万口水井
And where the bison have dug, the fox now spots an opportunity. 在美洲野牛挖过的地方狐狸也见缝插针
when cavers dug through several metres of loose rock 洞穴专家们在松散的岩层中 挖出了一条几十米深的通道