Q: Question: "If there is hydrogen present, what is not?" Context: "In the absence of atmospheric oxygen (O2), in deep geological conditions prevailing far away from Earth atmosphere, hydrogen (H2) is produced during the process of serpentinization by the anaerobic oxidation by the water protons (H+) of the ferrous (Fe2+) silicate present in the crystal lattice of the fayalite (Fe2SiO4, the olivine iron-endmember). The corresponding reaction leading to the formation of magnetite (Fe3O4), quartz (SiO2) and hydrogen (H2) is the following:" Answer:
A: atmospheric oxygen (O2)

Q: Question: "what is the second time period mentioned?" Context: "In the Early Middle Ages, from the end of the 4th century, the western extent of modern-day Switzerland was part of the territory of the Kings of the Burgundians. The Alemanni settled the Swiss plateau in the 5th century and the valleys of the Alps in the 8th century, forming Alemannia. Modern-day Switzerland was therefore then divided between the kingdoms of Alemannia and Burgundy. The entire region became part of the expanding Frankish Empire in the 6th century, following Clovis I's victory over the Alemanni at Tolbiac in 504 AD, and later Frankish domination of the Burgundians." Answer:
A: end of the 4th century

Q: Question: "Between 135 C.E. and 500 C.E. the Jewish population of Babylonia did what?" Context: "By the 1st century, Babylonia, to which Jews migrated to after the Babylonian conquest as well as after the Bar Kokhba revolt in 135 CE, already held a speedily growing population of an estimated 1,000,000 Jews, which increased to an estimated 2 million between the years 200 CE 500 CE, both by natural growth and by immigration of more Jews from the Land of Israel, making up about 1/6 of the world Jewish population at that era. At times conversion has accounted for a part of Jewish population growth. Some have claimed that in the 1st century of the Christian era, for example, the population more than doubled, from four to 810 million within the confines of the Roman Empire, in good part as a result of a wave of conversion." Answer:
A: doubled

Q: Question: "Rather than agree on the path to liberation, Buddhist schools do what?" Context: "Buddhist schools vary on the exact nature of the path to liberation, the importance and canonicity of various teachings and scriptures, and especially their respective practices. Buddhism denies a creator deity and posits that mundane deities such as Mahabrahma are misperceived to be a creator. The foundations of Buddhist tradition and practice are the Three Jewels: the Buddha, the Dharma (the teachings), and the Sangha (the community). Taking "refuge in the triple gem" has traditionally been a declaration and commitment to being on the Buddhist path, and in general distinguishes a Buddhist from a non-Buddhist. Other practices are Ten Meritorious Deeds including, giving charity to reduce the greediness; following ethical precepts; renouncing conventional living and becoming a monastic; the development of mindfulness and practice of meditation; cultivation of higher wisdom and discernment; study of scriptures; devotional practices; ceremonies; and in the Mahayana tradition, invocation of buddhas and bodhisattvas." Answer:
A:
vary on the exact nature