ANSWER:
spread and prevent is the answer.
not or no longer needed or useful;
If authors continue to talk about global warming in their books, there is a chance readers might start to try preventing global warming. They might plant more trees after seeing what happened in books. Or they might stop using things that released bad fuel into the air which causes the air to become polluted and result in global warming. In conclusion, after seeing what might happen in books, readers might try to prevent that to creat a better environment and future.
