Red Scare was the name given to the widespread fear of suspected Communists and radicals in the United States after World War I. The correct option among all the options given in the question is option "A". The first Red Scare happened in the United States during the 20th century and the reason was hyper nationalism in respect to World War I.
Imperialism is a political and military philosophy in which one country or government seeks to conquer other countries and societies and bring them under the control or influence of the invading country.
Imperialism is often associated with the economic theory of mercantilism, in which the conquering country (known as the metropole) becomes the center of manufacturing and production while the conquered countries (the colonies) become the suppliers of raw natural goods. Under a mercantilist system, the point of having colonies is to enrich the metropole.
Imperialism takes a number of forms. There's settler colonialism, where a metropole established colonies to gather raw goods or resources (New York and Jamestown are examples). There's religious imperialism, in which a country invades other countries for the purposes of spreading a religion (Spain was infamous for this) or establishes religious communities abroad (as in Massachusetts Bay).
Imperialism has also existed for ages and ages. The Romans are one famous example, but virtually every country in Western Europe (France, Britain, Spain, Portugal, Germany, Belgium, etc) had an empire at one point. But so did the Japanese, the Russians, the Zulus, and the Comanches.
Western imperialism in Asia involves the influence of people from Western Europe and associated states (such as Russia, Japan and the United States) in Asian territories and waters. Much of this process stemmed from the 15th-century search for trade routes to China that led directly to the Age of Discovery, and the introduction of early modern warfare into what Europeans first called the East Indies and later the Far East.
