Which interpretation about the author Chi-hao Fel is supported by this source

Which statement best summarizes the global depression?

Select all that apply. the tang dynasty interacted with foreigners by: a letting them buy property in china. b accusing them of corruption and the downfall of the dynasty. c trading with them, especially japan and korea. d teaching them to become monks. e attacking them with military forces.

What does the term “escalation” refer to?