What is one reason duplicate content can be problematic for SEO?

Duplicate content can be problematic for SEO because it can confuse search engines about which version of the content to index and rank. When multiple pages have the same or very similar content, search engines may struggle to determine the most relevant page to display in search results. This confusion can lead to diluted visibility for the pages involved, as search engines might divide the ranking signals (like backlinks and user engagement) among the duplicates instead of consolidating them to one page. As a result, none of the pages may achieve optimal ranking positions, ultimately impacting the site's overall SEO performance and traffic.

The other options do not accurately describe the primary issue caused by duplicate content. For instance, while duplicate content might indirectly influence backlinks, it does not inherently lower the number of backlinks. Additionally, duplicate content does not reduce the design quality of a webpage, nor does it have any role in ensuring that all content is unique.