Please choose the correct answer to the question: How do moose use a learned behavior to protect themselves?

Answer1: They have hollow hair to keep warm in the winter. Answer2: They roll in a pool of muddy water to avoid fly bites. Answer3: They have keen hearing to sense danger in the forest. Answer4: They use their wide hooves to prevent sinking in deep snow.

Answer format: answer1/answer2/answer3/answer4