subject of the formula

例句：

1. 1. The teacher asked the students to present their research on climate change.
   老师要求学生们展示他们对气候变化的研究。
2. 2.The book is about the history of the United States.
   这本书是关于美国历史的。
3. 3. The debate was about whether or not to build a new bridge.
   辩论是关于是否要建造一座新桥的。