instruction:
In this task, you are given a sentence and question which can be answered using the sentence. Your task is to answer the question using the information from the sentence. The answer to the question is unique and it is a continuous text span from the sentence.
question:
Sentence: While Ballard recuperates in the hospital , the released spirits , unharmed from the nuclear explosion , attack the city .
Question: who were released?
answer:
spirits

question:
Sentence: An '' optical image stabilizer '' , often abbreviated OIS , IS , or OS , is a mechanism used in a still camera or video camera that stabilizes the recorded image by varying the optical path to the sensor .
Question: how does something stabilize something?
answer:
by varying the optical path to the sensor

question:
Sentence: Although the area was known for its healthy waters at least since the late Middle Ages , the spa was officially founded in 1769 .
Question: when was something known for something?
answer:
since the late Middle Ages