同学你好，该知识点来自沪江网校《新概念英语第三册【随到随学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~

sound 有很多种意思，它在这里是形容词，意思是：可靠的
课文里把它翻译成“牢固的”没有问题哦~因为这里要表达的意思是：他们的地基很可靠。

We realized that they must have become unduly frightened by the rising flood, for their house, which had sound foundations, would have stood stoutly9 even if it had been almost submerged. 我们意识到他们一定是被不断上涨的洪水吓坏了，因为他们的房子地基牢固，即使洪水几乎灭顶也不会倒塌。

同学可以戳 [w]sound[/w] 学习更多相关知识~

期待助助的回答能帮到同学~祝学习进步~