Beijing Olympic champion Zou Kai won China\'s fourth gold medal in the gymnastics world championships here on Sunday with a clean performance on the horizontal bar, making China the top-ranking nation by medal tally. Zou notched 16.441 points in the final, outscoring his teammate Zhang Chenglong, defending champion who scored 16.366 and took the silver medal. Japan\'s top ace Kohei Uchimura, three-time all-around world champion, ranked third with a score of 16.333.