strong
Indicates that the text within the tags should be rendered with some form of strong emphasis. Authors should attempt to use the strong and em tags in place of the b, i and u tags, except where explicit control over text presentation is required.

attributes

id
Provides an element with a unique name within a single deck.
class
Affiliates an element with one or more classes.
xml:lang
Specifies the natural or formal language in which the document is written.