This topic examines the understanding of famous calligraphers and their works. Wang Xizhi, a famous calligrapher in the Eastern Jin Dynasty, is proficient in official script, cursive script, regular script and running script. Preface to the Lanting Pavilion is one of his most outstanding masterpieces, which is highly praised by calligraphers in past dynasties and is known as "the best running script in the world". So, the question should be C.