Something that could be considered one of the first examples of a Red Scare is
a. The actions towards socialist revolution by the NSC.
As @Andriansp putted it,
"Following the Russian revolution, United states undergone a massive worker's strike. Fearing the communist revolution, United states' attorney General allowed unwarranted arrest for those who is suspected as a communists"
b. is incorrect because that's referring to the space race and is irrelevant to this
c. is incorrect because Alger Hiss was convicted of being a soviet spy, not a communist
d. is incorrect because the IWW wanted to overthrow capitalism, which is the exact opposite of being afraid of communism almost
I hope this helps :)
