01Which attribute shows the browser's built-in play/pause/volume controls for <video> and <audio>?
02Why should you provide both MP4 and WebM <source> elements inside <video>?
03What does the poster attribute on a <video> element do?
04What attribute on <video> plays the video inline on iOS instead of going fullscreen?
05What file format do WebVTT caption tracks use and what extension do they have?