Problem: Zinc:

Zinc is a chemical element with symbol Zn and atomic number 30. It is the first element of group 12 of the periodic table. In some respects zinc is chemically similar to magnesium: its ion is of similar size and its only common oxidation state is +2. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest mineable amounts are found in Australia, Asia, and the United States. Zinc production includes froth flotation of the ore, roasting, and final extraction using electricity (electrowinning).

What is the atomic number for Zinc?
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A: 30


Problem: Christian:

Christianity remains the dominant religion in the Western World, where 70% are Christians. A 2011 Pew Research Center survey found that 76.2% of Europeans, 73.3% in Oceania, and about 86.0% in the Americas (90% in Latin America and 77.4% in North America) described themselves as Christians.

What do 86% of people in Oceania describe themselves as?
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A: unanswerable


Problem: London:

Greater London's population declined steadily in the decades after the Second World War, from an estimated peak of 8.6 million in 1939 to around 6.8 million in the 1980s. The principal ports for London moved downstream to Felixstowe and Tilbury, with the London Docklands area becoming a focus for regeneration, including the Canary Wharf development. This was borne out of London's ever-increasing role as a major international financial centre during the 1980s. The Thames Barrier was completed in the 1980s to protect London against tidal surges from the North Sea.

The main ports for London were relocated to where?
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A: Felixstowe and Tilbury


Problem: Textual criticism:

By 1939, in his Prolegomena for the Oxford Shakespeare, McKerrow had changed his mind about this approach, as he feared that a later edition – even if it contained authorial corrections – would "deviate more widely than the earliest print from the author's original manuscript." He therefore concluded that the correct procedure would be "produced by using the earliest "good" print as copy-text and inserting into it, from the first edition which contains them, such corrections as appear to us to be derived from the author." But, fearing the arbitrary exercise of editorial judgment, McKerrow stated that, having concluded that a later edition had substantive revisions attributable to the author, "we must accept all the alterations of that edition, saving any which seem obvious blunders or misprints."

McKerrow thinks we should only accept one revision for what reason?
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A:
unanswerable