Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.

[EX Q]: Passage: Studies on income inequality and growth have sometimes found evidence confirming the Kuznets curve hypothesis, which states that with economic development, inequality first increases, then decreases. Economist Thomas Piketty challenges this notion, claiming that from 1914 to 1945 wars and 'violent economic and political shocks' reduced inequality. Moreover, Piketty argues that the 'magical' Kuznets curve hypothesis, with its emphasis on the balancing of economic growth in the long run, cannot account for the significant increase in economic inequality throughout the developed world since the 1970s. Question: Who challenges the notion of the Kuznets curve hypothesis?
[EX A]: Thomas Piketty

[EX Q]: Passage: The city is served by the Tyne and Wear Metro, a system of suburban and underground railways covering much of Tyne and Wear. It was opened in five phases between 1980 and 1984, and was Britain's first urban light rail transit system; two extensions were opened in 1991 and 2002. It was developed from a combination of existing and newly built tracks and stations, with deep-level tunnels constructed through Newcastle city centre. A bridge was built across the Tyne, between Newcastle and Gateshead, and opened by Queen Elizabeth II in 1981. The network is operated by DB Regio on behalf of Nexus and carries over 37 million passengers a year, extending as far as Newcastle Airport, Tynemouth, South Shields and South Hylton in Sunderland. In 2004, the company Marconi designed and constructed the mobile radio system to the underground Metro system. The Metro system was the first in the UK to have mobile phone antennae installed in the tunnels. Question: What underground railways cover much of Tyne and Wear?
[EX A]: the Tyne and Wear Metro

[EX Q]: Passage: The Amazon rainforest (Portuguese: Floresta Amazônica or Amazônia; Spanish: Selva Amazónica, Amazonía or usually Amazonia; French: Forêt amazonienne; Dutch: Amazoneregenwoud), also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon basin of South America. This basin encompasses 7,000,000 square kilometres (2,700,000 sq mi), of which 5,500,000 square kilometres (2,100,000 sq mi) are covered by the rainforest. This region includes territory belonging to nine nations. The majority of the forest is contained within Brazil, with 60% of the rainforest, followed by Peru with 13%, Colombia with 10%, and with minor amounts in Venezuela, Ecuador, Bolivia, Guyana, Suriname and French Guiana. States or departments in four nations contain 'Amazonas' in their names. The Amazon represents over half of the planet's remaining rainforests, and comprises the largest and most biodiverse tract of tropical rainforest in the world, with an estimated 390 billion individual trees divided into 16,000 species. Question: How many square kilometers of rainforest is covered in the basin?
[EX A]:
5,500,000