1. Once, more than fifty hundred pairs of bald eagles nested across the country, but by 1960 that number had fallen below four hundred. 曾经有超过五千对白头海雕在全国各地筑巢，但到了1960年这一数字已降至四百以下。
2. Today's land tortoises constitute a single branch, deeply nested among branches consisting of aquatic turtles. 现在，陆龟构成一个独立的分支，完全被淹没在海龟的分支当中。
3. This is a nested iteration. 这是嵌套的迭代。
4. This can be done in a nested call. 可以在一个嵌套调用中完成这项操作。
