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.
Explanation:
Ivan the Great believed that ___MOSCOW, RUSSIA___ had replaced Rome and Constantinople as the new center of __THE CATHOLIC CHURCH/CHRISTIANITY____. He married a ___BYZANTINE/ROMAN____ princess and even took a title from ancient Rome-he called himself __TSAR___, which comes from the Latin word ____CEASAR____.
The Truman Doctrine was the first and clearest exercise of the policy of containment.
I hope this helps.
