英语语法分析

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。

One day, a bird came and nested in the tree.

有一天，一只鸟来了，在树上筑巢。

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。