How did the Chinese use existing defenses in building the Great Wall?

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.

The banking act of 1933, also known as the glass-steagall act, established the federal deposit insurance corporation (fdic), which a protected banks from failure by ensuring that the government would bail them out if necessary. b required american taxpayers to establish an account with a commercial bank. c protected depositors from financial losses when banks failed.

Drag and drop to identify the factors contributing to south asia high poverty rates. each phrase may be used once or not at all