Article: The most accurate timekeeping devices are atomic clocks, which are accurate to seconds in many millions of years, and are used to calibrate other clocks and timekeeping instruments. Atomic clocks use the frequency of electronic transitions in certain atoms to measure the second. One of the most common atoms used is caesium, most modern atomic clocks probe caesium with microwaves to determine the frequency of these electron vibrations. Since 1967, the International System of Measurements bases its unit of time, the second, on the properties of caesium atoms. SI defines the second as 9,192,631,770 cycles of the radiation that corresponds to the transition between two electron spin energy levels of the ground state of the 133Cs atom.

Question: How long has the International System of Measurements based the second on caesium?
Ans: Since 1967


Article: Most hunter-gatherers are nomadic or semi-nomadic and live in temporary settlements. Mobile communities typically construct shelters using impermanent building materials, or they may use natural rock shelters, where they are available.

Question: What is the permanence of hunter-gatherer settlements?
Ans: temporary


Article: Chopin was educated in the tradition of Beethoven, Haydn, Mozart and Clementi; he used Clementi's piano method with his own students. He was also influenced by Hummel's development of virtuoso, yet Mozartian, piano technique. He cited Bach and Mozart as the two most important composers in shaping his musical outlook. Chopin's early works are in the style of the "brilliant" keyboard pieces of his era as exemplified by the works of Ignaz Moscheles, Friedrich Kalkbrenner, and others. Less direct in the earlier period are the influences of Polish folk music and of Italian opera. Much of what became his typical style of ornamentation (for example, his fioriture) is taken from singing. His melodic lines were increasingly reminiscent of the modes and features of the music of his native country, such as drones.

Question: Whose piano method did Chopin use with his students?
Ans: Clementi


Article: The city of Bern or Berne (German: Bern, pronounced [bɛrn] ( listen); French: Berne [bɛʁn]; Italian: Berna [ˈbɛrna]; Romansh: Berna  [ˈbɛrnɐ] (help·info); Bernese German: Bärn [b̥æːrn]) is the de facto capital of Switzerland, referred to by the Swiss as their (e.g. in German) Bundesstadt, or "federal city".[note 1] With a population of 140,634 (November 2015), Bern is the fifth most populous city in Switzerland. The Bern agglomeration, which includes 36 municipalities, had a population of 406,900 in 2014. The metropolitan area had a population of 660,000 in 2000. Bern is also the capital of the Canton of Bern, the second most populous of Switzerland's cantons.

Question: Where is Bern located? 
Ans:
Switzerland