Correct Option: C

Data-X stores custom data. Buffer property is used to decide whether the output should be buffered or not. If autobuffering attribute is used, then the video will automatically begin to buffer even if it’s not set. It suggests to the browser that it should load as much of the resource as possible. As long as the browser’s own media cache isn’t full, it will keep on downloading. URL of an image is given by poster attribute until the user seek for it.