Correct option is (a) <aside>
Explanation: <aside> element can be used inside <article> or outside it also. When it is used inside <aticle> it contains information that is related to article. When <aside> is used outside <article>, it acts as container for content that is related to the whole page. Contact information of author/owner of a document can be provided by <address> tag. Footer typically contains information about author of the section, links to related documents or copyright data.