After the revolution in china the u. s. did something that upset soviet did they do?

We tried to bring both the Nationalist and Communist leaders together to come to some form of Compromise. We also left a delegation in Nanking to work with the new Communist regime, instead of fleeing back to Taiwan. China and Russia would soon fight over the fundamentals of Communism. We would not help matters, as anything that hurt Russia was seen as a good thing. 

The answer to the question is a.