Task: Question Answering
Input (English): Context: The nay - sayers of course say it does . All it says , however , is that there are longer - term trends that must be accounted for . And short - term developments that should scare us . Reports have come in recently of sightings of polar bears swimming from Alaska to find ice in the Arctic Ocean . Polar bears have been known to swim as much as 100 miles to find ice on which to hunt . 
Question: What may be the reason polar bears need ice ?
Output (English): They need ice to hunt .