This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Q: Passage: Goodluck Jonathan served as Nigeria's president till 16 April 2011, when a new presidential election in Nigeria was conducted. Jonathan of the PDP was declared the winner on 19 April 2011, having won the election with a total of 22,495,187 of the 39,469,484 votes cast, to stand ahead of Muhammadu Buhari from the main opposition party, the Congress for Progressive Change (CPC), which won 12,214,853 of the total votes cast. The international media reported the elections as having run smoothly with relatively little violence or voter fraud, in contrast to previous elections. Question: What was the main opposition political party in 2011?

A: Congress for Progressive Change
****
Q: Passage: Photorespiration can occur when the oxygen concentration is too high. Rubisco cannot distinguish between oxygen and carbon dioxide very well, so it can accidentally add O2 instead of CO2 to RuBP. This process reduces the efficiency of photosynthesis—it consumes ATP and oxygen, releases CO2, and produces no sugar. It can waste up to half the carbon fixed by the Calvin cycle. Several mechanisms have evolved in different lineages that raise the carbon dioxide concentration relative to oxygen within the chloroplast, increasing the efficiency of photosynthesis. These mechanisms are called carbon dioxide concentrating mechanisms, or CCMs. These include Crassulacean acid metabolism, C4 carbon fixation, and pyrenoids. Chloroplasts in C4 plants are notable as they exhibit a distinct chloroplast dimorphism. Question: When does photorespiration happen?

A: when the oxygen concentration is too high
****
Q: Passage: Whitehead and Russell had thought originally that Principia Mathematica would take a year to complete; it ended up taking them ten years. To add insult to injury, when it came time for publication, the three-volume work was so massive (more than 2,000 pages) and its audience so narrow (professional mathematicians) that it was initially published at a loss of 600 pounds, 300 of which was paid by Cambridge University Press, 200 by the Royal Society of London, and 50 apiece by Whitehead and Russell themselves. Despite the initial loss, today there is likely no major academic library in the world which does not hold a copy of Principia Mathematica. Question: Who paid to publish Principia Mathematica?

A:
Cambridge University Press
****