I want to know the answer to the following question:
What mountains surround the Sichuan basin to the North?
All the background I'm provided with is that "Since the Yangtze flows through the basin and then through the perilous Yangzi Gorges to eastern and southern China, Sichuan was a staging area for amphibious military forces and a refuge for political refugees.[citation needed]". Is that enough to answer the question?
Answer: no