How did the western allies respond to stalin's blockade of berlin?

a. they engaged in direct combat with the soviet union.
b. the built underground tunnels to supply west berlin.
c. they airlifted supplies into west berlin.
d. they allowed stalin to take control of west berlin.

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.