Analysis of test questions: This question mainly examines the historical facts of the harmonious relationship between the Tang Dynasty and the surrounding ethnic groups. Among the four options, option A reflects the relationship between Tang Dynasty and Uighur (later Uighur), option B reflects the relationship between Tang Dynasty and Dragon, option C reflects the relationship between Tang Dynasty and Tubo, and option D reflects the influence of Tang Dynasty culture on Japan. Therefore, options A, B and C reflect the harmonious ethnic relations in the Tang Dynasty, and option D reflects the diplomacy in the Tang Dynasty. So the answer is d.