Answer:
The use of parallelism allows Reagan to contrast democracy and communism.
Explanation:
According to the speech made by President Reagan in Berlin, he tries to convince the university students that communism restricts their freedom and how do racy would ensure their freedom.
President Reagan uses parallelism to support his message by helping him contrast democracy from communism.
Abstract nouns are essentially nouns that can be interpreted differently by different individuals, such as beauty or maturity. Going by this definition, the abstract noun in the given sentence should be "loyalty".