arbor hole

例句：

1. 1. The old oak tree has a large arbor hole that birds use to nest in.
   这棵老橡树有一个大树洞，鸟儿用来筑巢。
2. 2. The hikers found an arbor hole deep in the forest.
   徒步旅行者在森林深处发现了一个树洞。
3. 3. The children were curious about the mysterious arbor hole in the woods.
   孩子们对树林里那个神秘的树洞感到好奇。