What is the SEO purpose of adding links throughout your content?

Links to your product pages will boost your sales, as well as drive traﬃc to those pages.
Adding aﬃliate links throughout your content will drive more revenue for your business.
Links help establish you as a trustworthy source and drive traﬃc to your other content.
Links tell Google that your content is popular and that people are sharing it on social media.

The correct answer is:

Links help establish you as a trustworthy source and drive traﬃc to your other content.