Final answer:
Underlining and highlighting relevant passages in a book can be a helpful study technique, but underlining at least 50% of the text may not be necessary or beneficial.
Step-by-step explanation:
Underlining and highlighting relevant passages in a book can be a helpful study technique. It allows you to identify important information and make it easier to review later. However, underlining at least 50% of the text may not be necessary or beneficial. Instead, it is more effective to selectively underline key points, main ideas, or important quotes. This way, you can focus on the essential information and avoid overwhelming yourself with excessive underlining.