Problem: In 1997, OMB issued a Federal Register notice regarding revisions to the standards for the classification of federal data on race and ethnicity. OMB developed race and ethnic standards in order to provide "consistent data on race and ethnicity throughout the Federal Government. The development of the data standards stem in large measure from new responsibilities to enforce civil rights laws." Among the changes, OMB issued the instruction to "mark one or more races" after noting evidence of increasing numbers of interracial children and wanting to capture the diversity in a measurable way and having received requests by people who wanted to be able to acknowledge their or their children's full ancestry rather than identifying with only one group. Prior to this decision, the Census and other government data collections asked people to report only one race.
How many races were people asked to report in the US census prior to 1997?
The answer is the following: one

Problem: Another principal tool in the diagnosis of infectious disease is microscopy. Virtually all of the culture techniques discussed above rely, at some point, on microscopic examination for definitive identification of the infectious agent. Microscopy may be carried out with simple instruments, such as the compound light microscope, or with instruments as complex as an electron microscope. Samples obtained from patients may be viewed directly under the light microscope, and can often rapidly lead to identification. Microscopy is often also used in conjunction with biochemical staining techniques, and can be made exquisitely specific when used in combination with antibody based techniques. For example, the use of antibodies made artificially fluorescent (fluorescently labeled antibodies) can be directed to bind to and identify a specific antigens present on a pathogen. A fluorescence microscope is then used to detect fluorescently labeled antibodies bound to internalized antigens within clinical samples or cultured cells. This technique is especially useful in the diagnosis of viral diseases, where the light microscope is incapable of identifying a virus directly.
When is microscopy exquisitely specific?
The answer is the following: when used in combination with antibody based techniques.

Problem: By September 2008, average U.S. housing prices had declined by over 20% from their mid-2006 peak. As prices declined, borrowers with adjustable-rate mortgages could not refinance to avoid the higher payments associated with rising interest rates and began to default. During 2007, lenders began foreclosure proceedings on nearly 1.3 million properties, a 79% increase over 2006. This increased to 2.3 million in 2008, an 81% increase vs. 2007. By August 2008, 9.2% of all U.S. mortgages outstanding were either delinquent or in foreclosure. By September 2009, this had risen to 14.4%.
What was the percentage increase on foreclosure proceedings from 2007 to 2008?
The answer is the following: 81%

Problem: The aircraft carrier dramatically changed naval combat in World War II, because air power was becoming a significant factor in warfare. The advent of aircraft as focal weapons was driven by the superior range, flexibility and effectiveness of carrier-launched aircraft. They had higher range and precision than naval guns, making them highly effective. The versatility of the carrier was demonstrated in November 1940 when HMS Illustrious launched a long-range strike on the Italian fleet at their base in Taranto, signalling the beginning of the effective and highly mobile aircraft strikes. This operation incapacitated three of the six battleships at a cost of two torpedo bombers. World War II in the Pacific Ocean involved clashes between aircraft carrier fleets. The 1941 Japanese surprise attack on Pearl Harbor was a clear illustration of the power projection capability afforded by a large force of modern carriers. Concentrating six carriers in a single unit turned naval history about, as no other nation had fielded anything comparable. However, the vulnerability of carriers compared to traditional battleships when forced into a gun-range encounter was quickly illustrated by the sinking of HMS Glorious by German battleships during the Norwegian campaign in 1940.
What was signalled in 1940 when HMS Illustrious launched an strike on an Italian fleet?
The answer is the following:
the beginning of the effective and highly mobile aircraft strikes