Using radio button to accept Yes/No questions is best because the field accepts only one of the options. It is better than a dropdown because there are only two choices - either of them can be selected by a single click
Here is the code to create a yes/no radio button.
<input type=”radio” name”affirmative” value=”yes” checked> Yes </input> <input type=”radio” name”negative” value=”no”> No </input>
Also see: HTML Form input examples