Jan is a professional writer. His books, mostly based on managing relationships, achieving success at work, and keeping a work$-$life balance, are commonly read by people in their early $30$ s while they travel from work to office. Keeping this in mind, which of the following practices in designing these books will be effective?

minimal numbering of items or segments in the books

using plenty of white space in the books

making the books large enough so that they will not be lost

minimal use of headings within the books $.$

using general subject lines for the paragraphs