The correct answer is D) They brought about the end of the Red Scare by clearing several supposed radicals.
After World War I, the American government turned its intention to domestic communism. Citizens and the federal government were worried that citizens would try to overthrow the government in order to establish a communist (similar to what happened in Russia during the Russian Revolution).
This is why Mitchell Palmer (Attorney General of the US) ordered the raid of thousands of suspected communisms homes. After raiding the homes, very little evidence was found to show their guilty. This helped end the Red Scare, as it should that many of the people targeted by the federal government did not do anything wrong.