下列史实能够反映唐朝中外文化双向交流的是（   ）

①鉴真东渡 ②唐太宗被尊称为“天可汗” ③玄奘西行 ④遣唐使来华⑤陕西西安出土的唐代大食旅行者陶俑

    Davidson Black was a____(Canada) doctor who organized the excavation that led to the discovery of the bones in the Zhoukoudian____(cave) near Beijing. He was a specialist in the study of bones____it was his ambition to find and identify bones of early humans. His university was aware____the significance of his work. At first they gave him ample time to do his research, but____(late) they realized he was prepared to pursue it regardless of his students' needs and his____(teach) career, so they forbade him ____(travel) there any more. It was his assistant, Pei Wenzhong____made the discovery of these primitive bones and____(sharpen) tools. Davidson Black knew that his success was almost ____(entire) due to his assistant's systematic hard work.