Respuesta :
Mao Zedung got involved in the Korea War because he wanted to help re-take Seoul. The correct option among all the options that are given in the question is the third option or option "C". The other choices can be negated. I hope that this is the answer that you were looking for and it has helped you.
I believe the answer is: C. He was worried about his border with North Korea being in jeopardy.
Mao zedong feared that if he let the allied forces took control of north korea, the allied forces would be able to establish a navy base on that territory and exposed the chinese mainland from naval attack from north Korea. Because of this, he decided to help the north korean with both millitary soldiers and supplies.