The correct option is (b) <source>
For explanation I would say: <param> element defines parameters for <object> element. An element <picture> contains <source> element and <image>. <source> element in HTML specifies multiple media resource for <audio>, <video> and <picture> element. It is an empty element and is commonly used to serve same media content in multiple formats supported by different browsers. 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.