How did China's landscape play an important role in shaping its history?

How did China's landscape play an important role in shaping its history?
 
  a. Its mountains and deserts isolated the Chinese from advanced agrarian societies in other parts of Asia.
  b. Its vast stretches of rich farmland made it easy for agricultural advancement.
  c. Its eastern and western frontiers became the site of conflict between various Chinese peoples.
  d. Its earliest settlements developed in mountainous regions.
  e. Its hazardous terrain forged strong bonds between different groups who relied on each other for survival.