"7000 雅思单词100句PDF：辅助记忆方法大全"

The given content consists of four sentences that cover different topics. Sentence 1 discusses the American antelope or pronghorn, stating that it is a typical grassland animal found on the continent. Sentence 2 talks about Haley's comet and questions how many people who witnessed it in 1986 will live long enough to see its return in the twenty-first century. Sentence 3 highlights the findings of anthropologists who have discovered that certain emotions such as fear, happiness, sadness, and surprise are universally reflected in facial expressions among humans. Sentence 4 is incomplete and does not provide sufficient information for a summary. In conclusion, based on the given content, it is evident that the topics covered include the American antelope, Haley's comet, and the universality of facial expressions reflecting emotions. However, due to the incomplete nature of Sentence 4, it is impossible to comprehensively summarize the content within the strict requirement of 2000 words.