When the author says "200 million cameras track and identify citizens in real time to keep them in line," he employs which literary device?

Hyperbole

Explanation:

The literary device used in the given sentence is Hyperbole. Hyperbole is the exaggeration of the made claim. This helps in adding specific illustrated meaning to the given claim.  

The given sentence presents an exaggeration of '200 million cameras' on the citizens to 'track and identify' their activities. Joe Bubar in his article "No Hiding Your Face?" presents the picture of technological advancements that has helped the citizens but at the same time had violated the privacy of the citizens. The government's activity of keeping a record has been exaggerated and presented here.

"the tune the he might never know again." this part build anticipation. dexter got extremely happy by the piano tune. he could see what he was living at that moment in his life throught this feeling. the reader might want to learn more about his happy life. in fact, he called it a state of   'ecstasy'. the fact that he had got in a mood of intense appreciation and that everything about him was extremely bright and glamorous might lead the reader to feel that this state of happiness may not last long. the two parts from the excerpt that exemplify the anticipation are: " the sound of the "; " it was a know again."