This national leader defeated chiang kai-shek for control of china in 1949.

Mao Zedong

Explanation:

Chiang Kai-shek was leader of the Nationalists, and leader of China for some time. He last the final battle though for the rule over China, and the man responsible for that was Mao Zedong. Mao Zedong was the leader of the Communist. Once he managed to gain control over China, he was quick to assure that his position is secure on the long run, so he started to eliminate everyone that was a threat or seemed that it might be a threat. After this was all done, Mao started to implement his ideology, which was the communist ideology. He made China one of the major communist countries, and he implemented numerous ideas of his, unfortunately they resulted in the death of millions of Chinese people. His legacy still lives on in the present though, with the Communist Party still being in full control of China and it seems that it will be that way for long time.

a is the answer i believe.