Final answer:
To make the "Non-Smoking" button the default selection, the "checked" attribute should be added to the input element for the Non-Smoking option in the HTML of the form.
Step-by-step explanation:
To make the "Non-Smoking" button the default selected button in a form, you need to set the "checked" attribute on the relevant input element. Assuming you're working with HTML and possibly JavaScript, here's how you would typically do it in HTML:
<input type="radio" name="smoking" value="non-smoking" checked> Non-Smoking<br>
<input type="radio" name="smoking" value=smoking> Smoking
By including the "checked" attribute on the Non-Smoking button, the browser will load with this option pre-selected. This improves the user experience by making the presumed default choice clear and saves the user a click if Non-Smoking is indeed their choice.