When full, a saguaro stem can store up to five tonnes of water 吸饱水后 弁庆柱的茎干中 已储存了5吨左右的水
when the little there is is locked up as ice. 那里仅有的一点水也结成了冰
And when sulphuric acid dissolves limestone 硫酸在溶解石灰岩的同时
When the first explorers descended, 第一批探险家进入这个洞后
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
When the nearest exit may be hundreds of metres or more away, 最近的出口可能远在 几百米之外或者更远的地方