What are some examples and non-examples of sourcing?

The photograph shows children in germany after wwi. the photograph was most likely taken to show?

Ihat was “reborn” during the renaissance?

The rise of advertising in the 1920s. i am good with seeing how advertisements shape the roaring twenties and how it developed a new way of life through modern days. but i am not sure what the details of advertising in the 1920s were. if possible can you send me links (preferrably credential links) to sources that maybe show like the first company to start advertising through the radio, how advertising benefits (statistics graphs), etc.