In which excerpt from the text does kennedy most clearly acknowledge the viewpoint that no system of government is ideal?

a.) "there are many people in the world who really don't understand, or say they don't, what is the great issue between the free world and the communist world."

b.) "when that day finally comes, as it will, the people of west berlin can take sober satisfaction in the fact that they were in the front lines for almost two decades."

c.) "freedom has many difficulties and democracy is not perfect, but we have never had to put a wall up to keep our people in, to prevent them from leaving us."

d.) "i know of no town, no city, that has been besieged for 18 years that still lives with the vitality and the force, and the hope and the determination of the city of west berlin."