The correct option is (a) <bgsound>
The best I can explain: <bgsound> element only used by Internet Explorer is Background Sound element. It sets up a sound file to play in background while the page is used. We use <audio> instead of this element. <acronym> element which has been removed from HTML5 indicates sequence of characters. <blink> is a non-standard element which causes text to flash slowly. <audio> element is used to play audio clip.