Problem: Race (human categorization):

The 1775 treatise "The Natural Varieties of Mankind", by Johann Friedrich Blumenbach proposed five major divisions: the Caucasoid race, Mongoloid race, Ethiopian race (later termed Negroid, and not to be confused with the narrower Ethiopid race), American Indian race, and Malayan race, but he did not propose any hierarchy among the races. Blumenbach also noted the graded transition in appearances from one group to adjacent groups and suggested that "one variety of mankind does so sensibly pass into the other, that you cannot mark out the limits between them".

What can one not mark between the variety of mankind?
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A: limits

Problem: Hard rock:

In the late 1960s, the term heavy metal was used interchangeably with hard rock, but gradually began to be used to describe music played with even more volume and intensity. While hard rock maintained a bluesy rock and roll identity, including some swing in the back beat and riffs that tended to outline chord progressions in their hooks, heavy metal's riffs often functioned as stand-alone melodies and had no swing in them. Heavy metal took on "darker" characteristics after Black Sabbath's breakthrough at the beginning of the 1970s. In the 1980s it developed a number of subgenres, often termed extreme metal, some of which were influenced by hardcore punk, and which further differentiated the two styles. Despite this differentiation, hard rock and heavy metal have existed side by side, with bands frequently standing on the boundary of, or crossing between, the genres.

Hard rock is differentiated from heavy metal by containing more of an influence of what genre?
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A: bluesy

Problem: Ministry of Defence (United Kingdom):

The MoD states that its principal objectives are to defend the United Kingdom of Great Britain and Northern Ireland and its interests and to strengthen international peace and stability. With the collapse of the Soviet Union and the end of the Cold War, the MoD does not foresee any short-term conventional military threat; rather, it has identified weapons of mass destruction, international terrorism, and failed and failing states as the overriding threats to Britain's interests. The MoD also manages day-to-day running of the armed forces, contingency planning and defence procurement.

What are the threats that the MoD has identified?
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A: weapons of mass destruction, international terrorism, and failed and failing states

Problem: Aircraft carrier:

With the deactivation of USS Enterprise in December 2012, the U.S. fleet comprises 10 supercarriers. The House Armed Services Seapower subcommittee on 24 July 2007, recommended seven or maybe eight new carriers (one every four years). However, the debate has deepened over budgeting for the $1214.5 billion (plus $12 billion for development and research) for the 100,000 ton Gerald R. Ford-class carrier (estimated service 2016) compared to the smaller $2 billion 45,000 ton America-class amphibious assault ships, which are able to deploy squadrons of F-35Bs. The first of this class, USS America, is now in active service with another, USS Tripoli, under construction and 9 more are planned.

What class does the USS America belong to?
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A:
America-class amphibious assault ships