Read the following context and choose the best option to answer the question.
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 ?
Options: 
- They need ice to eat for the hydration .
 - None of the above choices .
 - They need ice to cool off after hunting .
 - They need ice to hunt .


They need ice to hunt .