1- The correct answer is C. The United States countered Soviet influence in Asia and Africa by sending both economic and (in cases) military aid to the colonial powers to fight communism.
So it was that the United States supported France in the Indochina War, collaborated with South Korea and became involved in the Angolan Civil War, among many other events.
2- The correct answer is A. McCarthysm was able to spread so easily in the United States because the Rosenberg trial led the public to believe there were more Communists in the country.
The fierce fighting of the Soviet and American sides originated real and imaginary fears, that made see enemies everywhere, even within the same Department of State of the United States, where a Marxist conspiracy was denounced by the Catholic senator from Wisconsin, Joseph McCarthy, in February 1950.
Soon, all America was in a state of panic. Many people were object of suspicion and victims of the adjudication of crimes of treason against their country. The list of suspects grew due to the denunciation of the communists themselves, who were forced to confess the identity of other comrades, to save themselves.
A famous case was that of the Rosenbergs in 1953, who were part of the Communist Party of the United States, and were accused of being informers of the Soviets and of giving them nuclear secrets. Both were executed in the electric chair, after a dubious trial, supported by the confession of a brother of the woman, also involved.