Which of the following can a search engine understand what your page is about?

The title tag  is the correct answer.

Explanation:

In the following question there is some detail that is the options are missing:

The title tag of the pages or the websites helps the search engines to know what types of details contained in your pages or the website. The title of the page of the website can help the users and the search engines is what type of information or data on your page. So, that's why the following option is true.

answerdestination end device address;