铁匠正在给马钉新的马蹄铁。

The farrier is nailing a new ___horseshoe to the horse's hoof.

教室里的座位排成了马蹄形，方便学生们互动。

The chairs in the classroom were arranged in a ___horseshoe shape to encourage student interaction.

他在谷仓门上挂了一个马蹄铁以求好运。

He hung a ___horseshoe on the barn door for good luck.