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: 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?
[A]: 21


[Q]: Passage: The dominant land plant species of the time were gymnosperms, which are vascular, cone-bearing, non-flowering plants such as conifers that produce seeds without a coating. This is opposed to the earth's current flora, in which the dominant land plants in terms of number of species are angiosperms. One particular plant genus, Ginkgo, is thought to have evolved at this time and is represented today by a single species, Ginkgo biloba. As well, the extant genus Sequoia is believed to have evolved in the Mesozoic. Question: What was the dominant plant species of the Mesozoic?
[A]: gymnosperms


[Q]: Passage: The gut is generally an almost straight tube supported by the mesenteries (vertical partitions within segments), and ends with the anus on the underside of the pygidium. However, in members of the tube-dwelling family Siboglinidae the gut is blocked by a swollen lining that houses symbiotic bacteria, which can make up 15% of the worms' total weight. The bacteria convert inorganic matter – such as hydrogen sulfide and carbon dioxide from hydrothermal vents, or methane from seeps – to organic matter that feeds themselves and their hosts, while the worms extend their palps into the gas flows to absorb the gases needed by the bacteria. Question: How much of a Siboglinidae's weight is symbiotic bacteria?
[A]:
15%