Answer:
The two cities on China's coast that were owned by European nations until the 1990s and were returned to China as specially governed regions are:
1- Hong Kong: Prior to being returned to China in 1997 as a Special Administrative Region (SAR) in accordance with the "one country, two systems" principle, Hong Kong was a British colony.
2- Macau: Macau was a Portuguese colony until 1999 when it was returned to China and also became a Special Administrative Region (SAR) with a similar arrangement to Hong Kong.
Both Hong Kong and Macau have a high degree of autonomy and maintain separate legal, economic, and political systems compared to mainland China.