Guests attend the opening ceremony of celebrating activities for the 100th anniversary of the founding of the Communist Party of China (CPC) and the 24th anniversary of Hong Kong's return to the motherland, at Hong Kong Convention and Exhibition Center in Hong Kong, south China, July 1, 2021. A series of celebrations were organized across Hong Kong, including parades of buses and fishing vessels. A commemorative movie named "1921" is on the big screens in multiple cinemas. [Photo by Lui Siu Wai/Xinhua]