What are the reasons for the political changes in kathmandu valley according to the medieval age?

Aresearcher is making an argument that the increase in nuclear weapons led to distrust between americans and soviet citizens

There are traits like blood type and eye color, and others like speaking english or having a scar. what are the terms used to describe these different types of traits? how are each defined?

Bonus question: according to wikipedia, in chinese philosophy yin and yang "describes how seemingly opposite or contrary forces may actually be complementary, interconnected, and interdependent." what are some examples from the story that amy tan may have intentionally incorporated elements of yin and yang philosophy into this story? select 2.