A four-month-old panda cub, Bei Bei, has been introduced to the media at the Smithsonian National Zoo. <br />The cub, whose twin brother did not survive, was just 4oz (113g) at birth. <br />He now weighs 17.5lb (8kg). <br />He and his two-year-old sister Bao Bao belong to China, and will go there when they turn four years old to join the breeding programme there.
