Which of the following are valid ways to associate custom data with an HTML5 element?

Which

You want to create a link for your website allowing users to email the webmaster. How will you implement this if the webmaster's email address is webmaster@xcompany.com?

What does the icon attribute of the HTML5 command tag define? Click Me!

How can audio files be played in HTML5? var sound = new Audio('file.wav');

You are writing the code for an HTML form and you want the browser to retain the form's input values. That is, if a user submits the form and presses the browser's back button, the fully populated form is displayed instead of a blank form. Which of the following HTML 5 attributes will you use?

Which is true about the placeholder attribute of <input> elements?

After the browser fires an `updateready` event, which of the following is true?

True or False: You can place a footer tag inside of a footer tag.

If IE8 doesn't recognize an element (such as <article>), what will it do with that element?

Which tag's positioning is independent of the main flow of the document?