I need to make sure that proper nouns are kept as they are. The task says "proper nouns stay", so Anand Kumar and the book title remain unchanged. Also, the book title is in quotes, so those stay.
"Easy to search: The PDF can be easily searched, making it easy to find specific topics and concepts." Control Systems Anand Kumar Pdf Free Download
Then there's "Library" as the third alternative. The original lists only one option here, but maybe the user considers "Library" as a single option. Wait, the task is to look for terms with three options. So maybe the original text doesn't have exactly three except for "Buy the hardcopy..." and "E-book stores...". Since those have two options each, perhaps the user expects me to add a third one to make it three. Let me do that. I need to make sure that proper nouns are kept as they are