Final answer:
The year when the subject slid into decay and chaos corresponds to the decline of cultural and artistic movements covered in the period from 1900 to 1940. The term 'decay and chaos' is subjective but is likely referring to the end of the Harlem Renaissance around 1930, marking a period of decline in cultural vibrancy due to the onset of the Great Depression.
Step-by-step explanation:
A World in Turmoil (1900-1940)
The year when the subject slide into decay and chaos is most likely referring to a specific historical or artistic period that underwent significant decline or disruption. The provided timeline hints at various art movements and historical events that took place between 1900 and 1940, such as Cubism, American Modernism, and the Harlem Renaissance. However, the term 'decay and chaos' is subjective and could refer to different moments within this timeframe, depending on the context. The closest related event is the Harlem Renaissance ending around 1930s, which could symbolize a cultural decay or decline in activity. Hence, if the question relates to cultural and artistic movements, 1930 is perhaps the most fitting answer from the available options.
To determine the correct year more precisely, it would be necessary to know the specific 'subject' the question refers to since several movements and historical periods are listed in the overview. Without additional context, 1930 may symbolize the beginning of decline for the cultural vibrancy and artistic output associated with movements like the Harlem Renaissance, which faded as the Great Depression took hold.