Final answer:
The Red Scare of 1919 led to increased government surveillance in the United States.
Step-by-step explanation:
The correct cause and effect relationship regarding the Red Scare of 1919 is option a) The Red Scare led to increased government surveillance.
During the Red Scare, there was a heightened fear of communist revolution and radicalism in the United States. This fear led to increased government surveillance to monitor and identify potential threats. The government implemented measures such as the Palmer Raids, which targeted suspected radicals and conducted warrantless searches.