The answer is b. When mass production became possible. hope that helps!
Assimilate singing and dancing with spoken dramatic action in any given location
<span>A short musical idea associated with a person, object, or thought, used by Richard Wagner in his operas, is called leitmotif.
It is a musical phrase that is usually very short, and appears constantly throughout an opera or something else each time a person associated with it appears on the scene. Richard Wagner used leitmotifs quite often, and they can especially be found in his Der Ring des Nibelungen.
</span>
The control channel is the wireless channel used to set up and disengage a call, so a text message might make it through even when a network’s voice channels are too overloaded to handle additional calls.