Here's a problem to solve: Polar bears are very heavy. About half of a polar bear's mass is fat. How does this adaptation most help a polar bear as it hunts in the Arctic Ocean?

Among the 4 following options, which is the correct answer?

- A: Fat makes the polar bear large.
 
- B: Fat makes the polar bear slippery.
 
- C: Fat helps the polar bear run on ice.
 
- D: Fat helps the polar bear float in water.
 