题干分析：在乌鲁布伦沉船中发现剑的含义。

原文定位：

P: So we've been talking about cetaceans, marine mammals like whales and dolphins. Are there any questions before we leave the topic?

S: Yeah, I've been reading about these times when cetaceans are found stuck on ocean beaches. They call it Stranding.……I mean, like sometimes 100 or more animals are found stranded on beaches. So what causes that? 

P: Strandings are often in the news, especially mass strandings like you mentioned. We're not really sure why this happens, but several hypotheses have been proposed. The first hypothesis……

选项分析：考察问答考点、并列考点。文章开头问学员关于海洋里的哺乳动物还有没有什么想问的，学生提到搁浅，并问为什么会有大量动物搁浅的现象，教授就回答有多个并列的假说，也就是之后整篇文章的主题，可知应选择C选项。A、B、D选项均未提及。