The correct answer is (a) <object>
Explanation: An external resource is represented by <object> element that can be treated as image, nested browsing context or a resource to be handled by plugin. It includes various attributes like archive, border, classid, codebase, codetype etc. <source> element specifies multimedia resources for pictures, audio etc. <param> element defines parameters for <object> element. An element <picture> contains <source> element and <image>.