His calligraphy works are called "the best running script in the world", and the calligrapher known as "the saint of calligraphy" is A. Wang Xizhi B. Yan Zhenqing C. Ou Yangxun D.

Test analysis: First, you can determine the calligrapher of option A and BCD. The first two are mainly regular script. Although Ou Yangxun has excellent running script, he is not a "saint of books" or "the best running script in the world", while Huai Su is famous for cursive script.