According to common sense, when Yang Guifei died in Maweipo, the tragedy was completed, but the author was ingenious. He wrote Xuanzong's thoughts on Yang Fei on his way to Sichuan, back to Beijing and back to Chang 'an, and described the emotional activities of the characters in detail, which promoted the further development of the plot. Among them, options A and B are about the grief on the way to Lucky Shu, and option D is about the infinite yearning after returning to Chang 'an. The answer is C.