four body problem

例句：

1. 1. The four-body problem is a complex issue that requires careful consideration.
   四体问题是一个复杂的问题，需要仔细考虑。
2. 2.The four-body problem has been a topic of interest for decades.
   四体问题已经是一个几十年来一直感兴趣的话题。
3. 3.The four-body problem is still not fully understood, despite years of research.
   尽管经过多年的研究，四体问题仍然没有完全被理解。