He refers to the story from the Sermon on the Mount about how houses built on sand fall, while those built on rock remain standing.

他引用的是“登山宝训”的故事，里面说，建在沙上的房子会倒，建在岩石上的房子依然屹立。

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The sea may rise or the land may fall; either way the sand dunes will be gone in a short time.

海平面可能会升高，或者陆地可能会下降；不论发生哪种情况，沙丘都将很快消失。

《柯林斯英汉双解大词典》

As she pulls the shoes out, the box with the sandwiches in it breaks open and the ham, the cheese, and the bread slices fall into the sand.

当她把鞋子拿出来的时候，装着三明治的盒子打开了，火腿、奶酪和面包片都掉在了沙子里。

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But he had got over it, practising his moves first on boulders from which he could fall five feet onto sand, gradually working higher, until some hundred feet up he could confidently climb with his palms open and relaxed, as calmly as if he was walking to the store.

ECONOMIST: John Bachar, free-climber, died on July 5th, aged 52