Polar bears are good at 1. , but they prefer to stay on top of the ice. They mainly eat seals, which can be hard to catch. Fortunately, polar bears' white coloring helps them 2. in the icy surroundings. However, polar bears' hairs aren't actually white. Their long outer hairs are mostly hollow and transparent. The air spaces in the hairs scatter 3. of all colors. Therefore, we look at polar bears and see the color white.
Some scientists believe the polar bear was once a close 4. to the brown bear. They think that, over time, polar bears moved to the Arctic. There, they 5. to their surroundings slowly.

1. swimming
2. hide
3. light
4. relative
5. adapted