Why did early civilizations begin in river valleys?

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.

Most members of the socialist party of america believed that the government should protect workers by: a.) operating big businesses. b.) outlawing strikes. c.) outlawing unions. d.) all of the above.

What event involving the maine motivated the united states to go to war with spain? it exploded in cuba. it was hijacked in the philippines. it exploded in panama. it was hijacked in puerto rico.