QUES: AAA battalions were also used to help suppress ground targets. Their larger 90 mm M3 gun would prove, as did the eighty-eight, to make an excellent anti-tank gun as well, and was widely used late in the war in this role. Also available to the Americans at the start of the war was the 120 mm M1 gun stratosphere gun, which was the most powerful AA gun with an impressive 60,000 ft (18 km) altitude capability. No 120 M1 was ever fired at an enemy aircraft. The 90 mm and 120 mm guns would continue to be used into the 1950s.

What decade were the 90 and 120 millimeter guns used until?
What is the answer?
ANS: 1950s
QUES: There are several types of multi-color white LEDs: di-, tri-, and tetrachromatic white LEDs. Several key factors that play among these different methods, include color stability, color rendering capability, and luminous efficacy. Often, higher efficiency will mean lower color rendering, presenting a trade-off between the luminous efficacy and color rendering. For example, the dichromatic white LEDs have the best luminous efficacy (120 lm/W), but the lowest color rendering capability. However, although tetrachromatic white LEDs have excellent color rendering capability, they often have poor luminous efficacy. Trichromatic white LEDs are in between, having both good luminous efficacy (>70 lm/W) and fair color rendering capability.

What is a factor that may be different in the various types of multi-color red LEDs?
What is the answer?
ANS: unanswerable
QUES: The state government left Philadelphia in 1799, and the federal government was moved to Washington, DC in 1800 with completion of the White House and Capitol. The city remained the young nation's largest with a population of nearly 50,000 at the turn of the 19th century; it was a financial and cultural center. Before 1800, its free black community founded the African Methodist Episcopal Church (AME), the first independent black denomination in the country, and the first black Episcopal Church. The free black community also established many schools for its children, with the help of Quakers. New York City soon surpassed Philadelphia in population, but with the construction of roads, canals, and railroads, Philadelphia became the first major industrial city in the United States.

When did the US government leave Philadelphia for D.C.?
What is the answer?
ANS:
1799