Which business letter feature is found at the top of the page?

The correct answer is the heading of the letter.

Explanation:

To begin with, the heading of a business letter is the part of it that shows who the sender is by giving information about him, like the sender's company, name and address. It also may include the date of writing as well.

Secondly, the heading is the part that goes in the top of the page due to the fact that is used to let the reader knows who wrote the letter and to whom the response must be sent.

The heading goes at the very top of the page, along with your name and address. So heading is correct. Good luck.