Part 1: Introduce the origin and development (50 tokens)
Part 2: Summarize the current situation in the world(150 tokens), including types, advantages, disadvantages, etc
Part 3: Provide your outlook and suggestions (100 tokens). Should be HIGH QUALITY, i.e. must include at least one chart or image and in-depth discussion; must use primary and scholarly secondary sources; must show evidence of significant additional research; Content must be true to fact and match the stated requirements. .
