This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Q: Passage: Eritrea has achieved significant improvements in health care and is one of the few countries to be on target to meet its Millennium Development Goal (MDG) targets in health, in particular child health. Life expectancy at birth has increased from 39.1 in 1960 to 59.5 years in 2008, maternal and child mortality rates have dropped dramatically and the health infrastructure has been expanded. Due to Eritrea's relative isolation, information and resources are extremely limited and according to the World Health Organisation (WHO) found in 2008 average life expectancy to be slightly less than 63 years. Immunisation and child nutrition has been tackled by working closely with schools in a multi-sectoral approach; the number of children vaccinated against measles almost doubled in seven years, from 40.7% to 78.5% and the underweight prevalence among children decreased by 12% in 1995–2002 (severe underweight prevalence by 28%). The National Malaria Protection Unit of the Ministry of Health has registered tremendous improvements in reducing malarial mortality by as much as 85% and the number of cases by 92% between 1998 and 2006. The Eritrean government has banned female genital mutilation (FGM), saying the practice was painful and put women at risk of life-threatening health problems.

A: In what year was female genital mutilation banned in Eretria?
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Q: Passage: In 1987, in Canada, Elizabeth publicly supported politically divisive constitutional amendments, prompting criticism from opponents of the proposed changes, including Pierre Trudeau. The same year, the elected Fijian government was deposed in a military coup. Elizabeth, as monarch of Fiji, supported the attempts of the Governor-General, Ratu Sir Penaia Ganilau, to assert executive power and negotiate a settlement. Coup leader Sitiveni Rabuka deposed Ganilau and declared Fiji a republic. By the start of 1991, republican feeling in Britain had risen because of press estimates of the Queen's private wealth—which were contradicted by the Palace—and reports of affairs and strained marriages among her extended family. The involvement of the younger royals in the charity game show It's a Royal Knockout was ridiculed and the Queen was the target of satire.

A: What government was Pierre Trudeau prime minister of in 1987?
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Q: Passage: Providing 25% of Namibia's revenue, mining is the single most important contributor to the economy. Namibia is the fourth largest exporter of non-fuel minerals in Africa and the world's fourth largest producer of uranium. There has been significant investment in uranium mining and Namibia is set to become the largest exporter of uranium by 2015. Rich alluvial diamond deposits make Namibia a primary source for gem-quality diamonds. While Namibia is known predominantly for its gem diamond and uranium deposits, a number of other minerals are extracted industrially such as lead, tungsten, gold, tin, fluorspar, manganese, marble, copper and zinc. There are offshore gas deposits in the Atlantic Ocean that are planned to be extracted in the future. According to "The Diamond Investigation", a book about the global diamond market, from 1978, De Beers, the largest diamond company, bought most of the Namibian diamonds, and would continue to do so, because "whatever government eventually comes to power they will need this revenue to survive".

A:
What is the second most important contributor to Namibia's economy?
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