Read the excerpt from excerpt from "Roberts Are Cool, But AI Is the Future." As these applications master the human language, AI will branch out into a variety of human endeavors, including the entertainment industry. Audiobooks (fiction and nonfiction narrated by authors and voiceover actors) are one of the largest-growing markets of the last three years. Once an afterthought of the publishing industry, audiobooks have become an increasingly profitable source of revenue for publishing companies. In 2018, about $940 million in audiobooks were sold—24.5 percent more than the previous year.

What is the tone of the excerpt?

informal

sincere

fearful

formal