Final answer:
Underlined words in an excerpt can provide emphasis, convey tone or mood, and indicate a shift in meaning or focus.
Step-by-step explanation:
The underlined words in an excerpt can affect the meaning of the text in various ways. They can provide emphasis on important information, convey the tone or mood of the passage, or indicate a shift in meaning or focus. For example, in the first excerpt from The Story-Book of Science by Jean Henri Fabre, the words 'sufficient reason' underline the importance and significance of the cause or symptom being discussed. In the second excerpt, the underlined words 'Ververt et Chartreuse', 'Belphegor', 'Heaven and Hell', 'Subterranean Voyage of Nicholas Klimm', and 'Chiromancy' suggest that these are the specific works that were read by the characters, highlighting their relevance to the story. Overall, underlined words can add nuance and depth to a text, enriching the reader's understanding of the meaning.