what is the correct way to add a default - styled button to an <a> tag?

Brief Explanations:

In HTML, to add a default - styled button - like look to an <a> tag, common practice is to use appropriate CSS classes. However, without seeing the actual content of the options clearly (as the text in the image is a bit blurry), generally, you would add a class that styles it as a button.

Answer:

There is not enough clear information in the image to determine the correct option among the ones shown.