Hello. You did not show the excerpt to which the question refers, which makes it impossible for that question to be answered accurately.
However, we can affirm that the sentence that you must select is one that shows statistical and / or scientific information, which allows the proof of a certain position or argument in relation to the text's theme. In that case, you should look for that type of information in the text you have.
Bernard ignores the conversation because he knows his fate would be sealed even more if he spoke up.
Explanation:
In the conversation between Mond, John and Helmholtz he knows that Mond will have the upper hand and anything that Bernard might say about what he was willing to do against the new society by reading the texts and organizing people who fail even further.
So he stays silent and only talks up to beg Mond to reduce his sentence for his crime of doing it but his friends had until them pretty much spilled the beans and had engaged in a discussion about the things they were doing.
In "the fun they had . " tommy finds a book. The book's pages are yellow and crinkly because it was an old book which excited nearly a 100 years ago when the books were printed in spite of being saved and shown in the television screen that tommy and Margie had.
Sentence 1 is the topic sentence. other sentences are based on 1 to support sentence 1, elaborating the topic sentence.