A:硝酸钠和金刚石
B:晶体硅和水晶
C:冰和干冰
D:苯和酒精
下列关于的说法正确的是( )
When leaders of Chinese mainland(大陆)and Taiwan met in Singapore for ________ first time since 1949, President Xi said, "Today will be remembered in _________ history."