常見例句Precautions of this sort are necessary, for it is impossible to foretell the exact nature of the difficulties which will confront the potholer.這種謹(jǐn)慎是必要的，因爲(wèi)洞穴勘探家將要麪臨的睏難的性質(zhì)， 是不可能預(yù)見的。 返回 potholer