Task: Question Answering
Input (English): 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: what   varies something?
Output (English): a mechanism ### An `` optical image stabilizer '' ### An `` optical image stabilizer '' , often abbreviated OIS , IS , or OS ### a mechanism used in a still camera or video camera