Answer:
C. The United States became less isolated from world events.
While the US brought up the idea of the League of Nations, at the end she did not join as congress failed to pass the US permission to be in it.
B. It showed that with a good motor and enough fuel, long-distance flight was safe.
This soon paved the way to the general public trusting and using planes as a mode of travel, and is reflected even today, in which most long distance travel is done by plane.
D. Only the Red Scare was about communists, but both became violent.
The Red Summer was about African descent, as opposed to the Red Scare, which was Soviet spies.
~