The correct answer is (b) <spacer>
For explanation I would say: HTML <strike> element places horizontal line through text. <spacer> is an obsolete HTML element. It allows insertion of empty spaces on pages. It was devised by Netscape to accomplish same effect as single-pixel layout image. <spacer> no longer supported by any major browser and same effects can be achieved by using CSS. <plaintext> element renders everything following start tag as raw text, without interpreting any HTML. <shadow> element is an obsolete part of web component which is used to shadow DOM objects.
