What is the most correct way to add CSS for just one/few pages in WordPress?

Question

WordPress

I want to include styles from bootstrap for only one page.
What is the best way to do this?
1) Make a custom page template?
2) Through some plugin?
3) Add styles for the entire site, but assign the class of a specific page to each so that it applies only to it?
Thank you!

Answer 1

I'm for the pattern.