TASK DEFINITION: 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.
PROBLEM: 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?

SOLUTION: 15%

PROBLEM: Passage: According to the Constitution of Estonia (Estonian: Põhiseadus) the supreme power of the state is vested in the people. The people exercise their supreme power of the state on the elections of the Riigikogu through citizens who have the right to vote. The supreme judicial power is vested in the Supreme Court or Riigikohus, with nineteen justices. The Chief Justice is appointed by the parliament for nine years on nomination by the president. The official Head of State is the President of Estonia, who gives assent to the laws passed by Riigikogu, also having the right of sending them back and proposing new laws. Question: Who holds supreme judicial power in Estonia?

SOLUTION: the Supreme Court or Riigikohus

PROBLEM: Passage: Greece's rail network is estimated to be at 2,548 km. Rail transport in Greece is operated by TrainOSE, a subsidiary of the Hellenic Railways Organization (OSE). Most of the country's network is standard gauge (1,565 km), while the country also has 983 km of narrow gauge. A total of 764 km of rail are electrified. Greece has rail connections with Bulgaria, the Republic of Macedonia and Turkey. A total of three suburban railway systems (Proastiakos) are in operation (in Athens, Thessaloniki and Patras), while one metro system is operational in Athens with another under construction. Question: Who is TrainOSE a subsidiary of?

SOLUTION:
the Hellenic Railways Organization