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.

Input: Consider Input: Passage: Northwestern has several housing options, including both traditional residence halls and residential colleges which gather together students who have a particular intellectual interest in common. Among the residential colleges are the Residential College of Cultural and Community Studies (CCS), Ayers College of Commerce and Industry, Jones Residential College (Arts), and Slivka Residential College (Science and Engineering). Dorms include 1835 Hinman, Bobb-McCulloch, Foster-Walker complex (commonly referred to as Plex), and several more. In Winter 2013, 39% of undergraduates were affiliated with a fraternity or sorority. Northwestern recognizes 21 fraternities and 18 sororities. Question: How many fraternities does Northwestern recognize?

Output: 21

Input: Consider Input: Passage: In November 1795, there was a debate in Parliament on the high price of corn and Burke wrote a memorandum to Pitt on the subject. In December Samuel Whitbread MP introduced a bill giving magistrates the power to fix minimum wages and Fox said he would vote for it. This debate probably led Burke to editing his memorandum, as there appeared a notice that Burke would soon publish a letter on the subject to the Secretary of the Board of Agriculture, Arthur Young; but he failed to complete it. These fragments were inserted into the memorandum after his death and published posthumously in 1800 as, Thoughts and Details on Scarcity. In it, Burke expounded "some of the doctrines of political economists bearing upon agriculture as a trade". Burke criticised policies such as maximum prices and state regulation of wages, and set out what the limits of government should be: Question: Who did Burke write to about the price of corn?

Output: Pitt

Input: Consider Input: Passage: Seismology: To better prepare for calamities, Zhang Heng invented a seismometer in 132 CE which provided instant alert to authorities in the capital Luoyang that an earthquake had occurred in a location indicated by a specific cardinal or ordinal direction. Although no tremors could be felt in the capital when Zhang told the court that an earthquake had just occurred in the northwest, a message came soon afterwards that an earthquake had indeed struck 400 km (248 mi) to 500 km (310 mi) northwest of Luoyang (in what is now modern Gansu). Zhang called his device the 'instrument for measuring the seasonal winds and the movements of the Earth' (Houfeng didong yi ), so-named because he and others thought that earthquakes were most likely caused by the enormous compression of trapped air. See Zhang's seismometer for further details. Question: What did the Chinese caused earthquakes?
Output: enormous compression of trapped air