What is a factor that led to the rise of mass culture in the 1920s?
a- installment buying
b- greater mobility across the nation
c- the migration from the cities to the suburbs
d- the harlem renaissance and rise of jazz music

Ineed because i cannot find the answers anywhere

Aresearcher proposes to conduct a study at a foreign site. the research has been determined to be exempt from the federal regulations by institutional policy. according to federal regulations, is review required at the foreign site? if a proposed study qualifies for exemption, federal regulations do not require review at the foreign site where it will be conducted but still require review at the u.s. site by the institution’s irb. if a proposed study qualifies for exemption, federal regulations do not require review at the foreign site where it will be conducted. if a proposed study qualifies for exemption, federal regulations do require review at the foreign site where it will be conducted. if a proposed study qualifies for exemption, federal regulations do not require review at the foreign site where it will be conducted, but still require review by the institutional official at the local site.

What has contributed to the growth of agriculture as big business in the midwest