instruction:
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.
question:
Passage: A elevator of this kind uses a vacuum on top of the cab and a valve on the top of the "shaft" to move the cab upwards and closes the valve in order to keep the cab at the same level. a diaphragm or a piston is used as a "brake" if there's a sudden increase in pressure avove the cab. however, to go down, it opens the valve so that the air can pressurize the top of the "shaft", allowing the cab to go down by its own weight. this also means that in case of a power failure, the cab will automatically go down. the "shaft" is made of acrilic, is always round, due to the shape of the vacuum pump turbine. in order to keep the air inside of the cab, rubber seals are used. due to technical limitations, these elevators have a low capacity. they usually allow 1-3 passengers and up to 525 lbs. Question: For sudden surges in pressure above the cab, what is used as a "brake"?
answer:
a diaphragm or a piston


question:
Passage: The breakup of the Carolingian Empire was accompanied by invasions, migrations, and raids by external foes. The Atlantic and northern shores were harassed by the Vikings, who also raided the British Isles and settled there as well as in Iceland. In 911, the Viking chieftain Rollo (d. c. 931) received permission from the Frankish King Charles the Simple (r. 898–922) to settle in what became Normandy.[Q] The eastern parts of the Frankish kingdoms, especially Germany and Italy, were under continual Magyar assault until the invader's defeat at the Battle of Lechfeld in 955. The breakup of the Abbasid dynasty meant that the Islamic world fragmented into smaller political states, some of which began expanding into Italy and Sicily, as well as over the Pyrenees into the southern parts of the Frankish kingdoms. Question: Who was king of the Franks in 899?
answer:
Charles the Simple


question:
Passage: The incorporation of the First Amendment establishment clause in the landmark case of Everson v. Board of Education has impacted the subsequent interpretation of the separation of church and state in regard to the state governments. Although upholding the state law in that case, which provided for public busing to private religious schools, the Supreme Court held that the First Amendment establishment clause was fully applicable to the state governments. A more recent case involving the application of this principle against the states was Board of Education of Kiryas Joel Village School District v. Grumet (1994). Question: When was the case of v. Grumet?
answer:

1994